1. Introduction

One of the most effective mechanisms for understanding an object of study is to segregate it, ‘for exclusively didactic purposes’, from the context in which it is situated and, once apprehended, to return it to the system to which it belongs. In this context, this article, without the slightest intention of exhausting the subject, proposes a reflection on customs law as an autonomous branch of law.

For this purpose, it is important to delimit certain premises and concepts under which the reflections will be presented. The analysis starts from the understanding that the expression ‘legal system’ can designate two distinct linguistic constructions: the prescriptive system of law – legislative texts – and the descriptive system concerned with those texts, legal science. In this article, ‘law’ refers to the set of prescriptive statements known as ‘positive law’, whereas ‘legal science’ refers to the descriptive discipline responsible for ‘describing the normative framework, ordering it, declaring its hierarchy, displaying its logical forms […] and offering its contents of meaning’ (Carvalho, 2013, p. 32). The present reflection therefore examines a possible ‘legal’ autonomy of customs law and a probable ‘scientific’ autonomy of customs law.

With this, the aim is to reduce sterile debates and understand the reasons why dealings pertaining to the control of the international movement of persons and goods have only more recently gained prominence in academia. Costa (2004) observes that the scarcity of doctrinal texts in Brazil is basically due to the absence of systematised legislation on the matter, a situation that is aggravated if one considers the multiple disciplines involved in customs matters.

Beyond abstract reflections on autonomy, this article also considers practical problems in dealings with national customs authorities. Many of those problems are connected with the still incipient systematisation of customs law as a distinct field.

First of all, it should be stated that, at least in Brazil, the most authoritative doctrine appears to converge on the position advanced by Sehn (2022), who treats customs law as an autonomous branch governing the control and supervision of the entry and exit of goods, vehicles and persons, as well as foreign trade more broadly. Galera Rodrigo (1995) similarly characterises customs law as a body of public-law rules with a protective function applicable to international trade in goods, together with the rules necessary for their effective application.

It should be emphasised that the present article seeks to understand the autonomy of customs law, considering Brazilian legal doctrine, with the intention of offering other countries a brief contribution to the understanding of customs law within their systems.

It should also be noted that customs law, like tax law, is a law of superposition, which incorporates various concepts and legal institutions shaped in other subsystems. Tax law, for example, borrows the institution of ‘private property’ from private law to define the incidence of taxes on property. Likewise, customs law makes use of legal institutions forged in other fields and, similarly, private law may make use of legal institutions from customs law. Customs law is, however, a branch of public law, especially because it encompasses rules governing the dealings of the state with individuals under its administration or even with foreigners who engage in international trade with the country and are subject to its sovereignty, if only to a small degree.

In the same way, it seems evident that customs law is subject to other guiding principles of various areas of public law, such as the principle of legality, legal certainty, proportionality (in supervision) and transparency. In the present work, however, the aim is to identify the fundamental postulates, that is, the ‘super principles’ of customs law, which are essential for understanding its autonomy. In this regard, two guiding principles deserve emphasis and constitute its basic pillars: (i) the principle of national interest and (ii) the principle of integration.

The principle of integration is easily inferred from the World Customs Organization’s Revised Kyoto Convention (WCO, 1999) and Harmonized System Convention (WCO, 1983), the World Trade Organization’s Customs Valuation Agreement (WTO, 1994a), and other WTO agreements, including the General Agreement on Tariffs and Trade 1994 (GATT) (WTO, 1994b) and the Trade Facilitation Agreement (WTO, 2013). This fundamental basis is left for analysis on another occasion. In this brief essay, it is worth devoting our attention to the principle of national interest.

As an order, law asserts itself as a system and reveals an ordering and a unity that prevents the dispersion of its norms, bringing them back to a few constitutive principles. Legal norms form a homogeneous and cohesive complex, relating to one another in such a way that each connects with the others, thereby configuring a systematic and coherent organisation. The system thus allows itself to be defined as an axiological or teleological order of general principles of law.

The legal system is not reducible to a set of legal rules, because rules alone lack the unifying connection required of a system. Nor is it merely a system of concepts: a legal system must achieve value-related adequacy and internal unity, whereas valuation remains implicit in a concept and is made explicit by a principle. Nor does it correspond to a simple set of legal institutions, because such institutions do not by themselves provide a unifying valuation. As Canaris (1996, p. 77) explains, a system is constituted by the internal ordering and interconnection of its elements rather than by their disconnected enumeration. Finally, a legal system is not simply an order of values, because a principle, unlike a value, indicates at least the direction of the legal consequence.

In the analysis of the ‘system’ of law, it is possible to observe that each of its ‘subsystems’ serves to regulate specific legal relationships, from which arises the need to recognise the existence of specific prescriptive statements intended to govern such relationships. Obviously, the legal order is one; however, what has conventionally been called ‘branches of law’ is structured through general principles specific to each branch. In this regard, legal principles can only be fully understood when the countervailing and limiting principles and the scope of application assigned to them are taken into consideration.

In this sense, it is the existence of specific principles that reveals the methodological need to divide law into ‘subsystems’, providing legal practitioners with an approach to, and an understanding of, law as a single and indivisible logical unity. However, it is well known that the ‘branches of law’ forge their own institutions or make use of institutions formed in other branches of law, almost always subjecting them to a ‘teleological adaptation’.

In undertaking such delineations, the classical division of law into public and private no longer proves appropriate for adequately indicating where the various legal disciplines should be placed. Within a legal order of a social character, public law and private law are not separated by a rigid boundary; on the contrary, they ‘tend to become confused with and to encroach upon one another’ (Radbruch, 1997, p. 256).

One may discern in customs law a certain ‘multifaceted’ character, insofar as the subsystem encompasses both the regulation of institutions proper to public law (such as those relating to the ‘administrative enforcement powers’) and those of private law, such as the regulation and legal definition of ‘customs value’. The very proposal of a universal nomenclature of goods illustrates this dual function: it serves both to define the rates applicable to customs duties and to identify products that must be subject to special import regimes, also to facilitate commercial relations between sellers and buyers, especially between countries with different languages.

There is no doubt that customs law governs its own legal institutions. The issue that must be examined, however, is whether customs law is endowed with specific principles capable of serving as pillars for the interpretation and integration of the norms of the ‘subsystem’, as well as of enabling an understanding of the legislation of the field and of illuminating hermeneutical work.

3. Customs law and the principle of the supremacy of the national interest

Legal principles are central norms that provide the logical and coherent structuring of the legal system. They are fundamental propositions that structure the legal order and are part of it. For this reason, it may be said that the legal system is a teleological order of legal principles and rules. Principles determine the substance of acts that are hierarchically inferior to them; they establish the ratio of legal rules and, therefore, are not addressed solely to legislators, but also to public authorities, judges and citizens.

Legal principles are endowed with two main functions: a positive function, whereby the principle serves as an illuminating point for the guidelines and content of legal regulation, as the source of the content of the norms that derive from it and that owe to it coherence and compatibility. They also have a negative function, which signifies the rejection of norms and commands that run counter to them. They exclude from the validity of law any conduct that is nonconforming or incompatible with their binding guidelines.

From the positive function, it may be observed that legal rules are, in some manner, applications of principles; they operate and give concreteness to principles. Precisely for this reason, the interpretation of rules is illuminated by guiding principles. On the other hand, considering their negative function, principles may only set aside, due to their plasticity and abstraction, situations identified within a ‘zone of negative certainty’, that is, those contents incompatible with their basic core of meaning.

In sum, legal principles perform a hermeneutical function of material content for the clarification of the meaning of certain provisions; they provide meaning for interpretation, establishing an evaluative direction, an axiological sense, while at the same time, imposing limits and content.

The identification of the guiding principles of a subsystem assumes a pivotal function, since it is they that must illuminate the interpretation of the norms governing the branch, as well as exercise a negative function. For this reason, the debate concerning the scientific autonomy of a given subsystem is fundamental to verify the proper and true meaning of legal norms. In this sense, it is important to ascertain whether, in fact, there exist specific guiding principles of customs law.

The notion of the ‘democratic state under the rule of law’ makes it possible to extract a material understanding grounded in the assertion that the essential purpose of the state lies in the pursuit of the common good and in the realisation of social justice. The democratic state under the rule of law is constituted to satisfy the needs of the community, to foster human dignity and the good of humankind, in line with what Rousseau (1996) had already advocated.

For the world of law, indeed, this is a legal concept whose concrete individualisation can only be found in positive law itself. The legal concept of ‘public interest’ concerns those public purposes/needs set out in the law; it translates those ‘interests’ entrusted by law to the care of the public administration, which must be pursued, and which establish a power/duty of action for the public administration.

In the modern democratic state under the rule of law, the idea of ‘public interest’ has been humanised, insofar as the state has come to be concerned with values regarded as essential to a dignified human existence. Indeed, the idea of public interest, in observance of the principle of human dignity, has come to encompass the aspiration for freedom with dignity, requiring from the state appropriate action to reduce social inequalities, bringing social wellbeing to society. In the democratic state under the rule of law, within a pluralist society, the ends that the state must pursue, as legally established, are broad and are no longer restricted to security, but cover almost everything related to the promotion of the common good (in a broader structural sense).

The juridicised idea of the ‘common good’, as a more indirect reference for state action, does not reduce it to the sum of the various ‘public interests’ conveyed by law. On the contrary, the legal concept of the ‘common good’ signifies the concerted result arising from the harmonisation and balancing of public interests (as a legal concept) submitted to the consideration of the public administration by the legal order. If the state exists for the pursuit of the ‘common good’, on the other hand, in a pluralist society there arises a multiplicity of public interests whose fulfilment must be articulated so that the ‘common good’ may be sought in an optimised manner. These diverse ends are translated juridically into powers/duties entrusted to the public administration for the pursuit of public interests recognised by the legal order; the diversity of such interests being expressed by the various centres of a pluralist public administration.

Public interest reflects needs already qualified as public by-laws, whether indirectly, through the regulation and organisation of the public administration, or directly, through the attribution of a certain and specific competence to this or that authority. To each of the bodies, entities, or units that participate in the public administration or that aim at the pursuit of the ‘common good’, there is legally attributed, at least, a singular ‘primary public interest’ to be achieved. The ‘primary public interest’ is that provided for by the law attributing power and that directly grounds the administrative decision of a given body, entity or unit.

The state attributes small spheres of power/duty to various bodies or units, which must thus safeguard specific primary public interests that, within this complex web of needs, in various situations, may even be placed in opposition to one another. It may be observed that Customs must attend to national treasury interests; however, this is obviously only one of the primary public interests granted to the sphere of competence of this administrative body, which is responsible for a range of public (national) interests of the pluralist society (gathered within the Brazilian state) that likewise merit protection.

The activities of the public administration in furtherance of the ‘common good’ are disseminated among the various organs of the state, along its different lines of action, and thus it is not possible to single out one organ as the one responsible for the pursuit of the ‘common good’. The need to pursue disparate ends will entail the necessary distribution of decision-making competences among differentiated administrative bodies and entities. Conversely, government ceases to be the apex of the bureaucratic pyramid and becomes part of a system dominated by ‘major services’ articulated in a network (such as education, health, transport and social security).

There is no longer a single public administration, but rather ‘public administrations’, among which relationships, conflicts, agreements and controversies develop that modify substantive administrative law and influence procedure. According to Giannini (1991), if only one administrative body were to attend to all the interests of state administration, some interests would be entirely sacrificed in furtherance of others that the body might consider, according to its own judgement, to be prevailing.

Customs public administration essentially pursues the ‘national interest’, which calls for action that is holistically favourable to the ‘common good’ of the nation-state, distinct from the isolated and unilateral view proper to a given primary public interest established by law and to be pursued by a particular body of the public administration. This idea of ‘national interest’ is multifaceted and diverse, insofar as, within the complex modern democratic state, in a pluralist society, it falls to the public administration to safeguard a diversified bundle of (public) interests.

The nation-state pursues diverse objectives; therefore, customs law must be guided by the ‘satisfaction of the national interest’, understood as the concerted composition of the most diverse public interests, which may even be misaligned. The ‘national public interest’ is nothing more than a moving equilibrium among public interests that are at times opposing, and there are as many multiple and equivalent aspects of this idea as there are probabilities of equilibria among opposing interests.

Various public interests are placed before the national state, often even contradictory among themselves, and the legally established ‘national public interest’ functions as a kind of synthesising interest, resulting from a balanced weighing of these various intervening public interests carried out by law. In the composition of the ‘national interest’, however, not even the private interests of nationals are set aside as opposed to the public interest, insofar as economic development itself may be, and usually is, a determining consideration; that is, the development of a national private enterprise may translate into national development. If, on the one hand, private enterprises seek to obtain profits, or at times merely to cover their costs, for customs law what matters is the protection of the ‘national interest’ (and not of a ‘national public interest’), within which political objectives of the most diverse kinds may be included.

Undoubtedly, the globalisation of capital in contemporary globalised society has been attracting international movements that seek to promote the facilitation of international trade. For this reason, international organisations systematically organise rounds of negotiations and foster the conclusion of treaties that may facilitate and encourage trade among peoples. In this context, the defence of treasury interests appears with marked prominence among the duties entrusted to customs authorities. It must be emphasised, however, that it does not fall to the customs administration merely to safeguard treasury interests, but, above all, to care for the national interest. For this reason, even private interests may not be disproportionately sacrificed to the detriment of the overarching purpose of promoting national economic development.

The idea of public interest, at least structurally, is conceived as a category opposed to that of private or individual interest. However, the structural idea of public interest is not to be confused with that of an interest common to all citizens. The ‘national interest’ refers to the ‘interest of the whole’, of the ‘social body itself’, which does not, however, coincide with the sum of individual interests peculiar to each person, nor, on the other hand, does it constitute an interest endowed with autonomous consciousness.

In this sense, the ‘national interest’ is an interest emerging from the existence of life in community, in which most individuals also recognise a direct and personal interest, whose ultimate beneficiary is the population of the state as a whole. Conversely, the ‘national interest’, structurally, views interests within a historical continuity, considering the ‘succession of generations’. It thus encompasses the present interests of individuals and groups, participants in the larger community in which they are embedded, as well as those who will succeed them in future generations.

Customs law takes as its fundamental foundation the defence of the national interest. In this vein, the guiding principle of customs law reveals itself as a kind of ‘principle of the supremacy of the national interest’, which obliges Customs, in the control of international trade, to cause the interests of the Brazilian people to prevail.

At times, the principle of the supremacy of the national interest calls for, for example, the defence of national development; at others, the defence of national health. More precisely, the ‘national interest’ is the concerted synthesis of the broad range of public interests and of the private interests of nationals, which is always that of the nation as a whole and which qualifies the overarching guiding principle of customs law. In sum, customs law has as its principal organising principle the ‘principle of the supremacy of the national interest’, comprehensive in scope by reason of the qualification of the interest it pursues.

The national pluralist society demands much more than mere treasury interest, or even interest in economic development. Obviously, in deference to legal certainty, customs officers must be guided by the power/duty conferred upon them by law, and observe the principle of legality. However, from a broader perspective, it may be observed that the pivotal guiding principle of customs law, which illuminates the interpretation of norms and makes it possible to exclude unlawfulness in ‘zones of negative certainty’, is the principle of the supremacy of the national interest.

4. The exercise of control and customs law

Border control is an essential manifestation of the defence of national sovereignty. In this sense, the essential core of customs law is constituted by norms that tend to regulate the entry and exit of goods from customs territories, as well as by norms intended to regulate the exercise of the control function (customs police power).

Several scholars propose addressing the question of autonomy from different analytical perspectives. Basaldúa (2018), for example, goes so far as to attribute a large part of the difficulties in ensuring autonomy for customs law to the absence of a univocal definition. It is relevant to verify the existence of a didactic autonomy of customs law, at least for academic and teaching purposes, and whether there truly exists a legal or scientific autonomy that allows for the identification of a subsystem of customs law endowed with its own concepts, legal institutions and principles.

Regarding legislative and didactic autonomy, Costa (2004) already recognises that the branch of customs law is easily ascertainable, since it derives from the simple fact of having a group of norms that present particular homogeneity in relation to their object. This allows for its separate study, even though, as the present work asserts, it is subject to principles of other branches of law. Thus, there is homogeneity in the norms that constitute the object of customs law, namely, the regulation of the movement of persons and goods within the customs territory, as well as of foreign trade.

On the other hand, as already analysed, the ‘principle of the supremacy of the national interest’ may already qualify the subsystem and must govern the interpretation of the legal rules that regulate customs and the customs function. However, customs cannot act in an arbitrary manner. This is because, if customs law has as its principle the supremacy of the national interest, it must, to the same extent, provide legal certainty for the regulated party.

Customs law can never disregard private interests in violation of the foundations of the rule of law. Customs law thus develops with due regard to the necessary defence of the national interest, in strict observance of the limits set by law (the principle of legality) and must likewise observe the principle of proportionality.

On the one hand, customs law outlines a series of functions to be performed by Customs in the defence of the national interest and, on the other, confers upon customs bodies a power of intervention in the private sphere that is limited and grounded in law. The power of action of Customs is therefore instrumental and is not justified, but rather as support for state action in the realisation of the national interest and must be understood as limited. The logic of the democratic state under the rule of law, which privileges the national interest in its action, likewise limits the possibilities of suppressing private liberty and property.

In this vein, to understand that the primary purpose of Customs is control, that is, the exercise of customs police power, indeed appears to be mistaken. The power/duty attributed to customs bodies is merely instrumental, and this occurs solely so that Customs may, in its action, act in furtherance of national interests and defend national sovereignty, within the precise limits established by law. There is no inherent power to identify the national interest; rather, this idea is revealed only within the exact terms established by law. It is the law that reveals the interest to be pursued in the exercise of customs police power. Control is merely the mechanism, within police action, to ensure the true purpose that is revealed only in law: the national interest.

On the other hand, several international treaties of the 20th and 21st centuries have already been concluded with the aim of promoting trade facilitation, so that economic development of nations might thereby be stimulated and the ‘national interest’ of the signatories ensured in a planet globalised by worldwide capital.

The International Monetary Fund (2001) reports that the growth of international trade relations materialises in a uniform progression of 6 per cent per year and is grounded in two major supporting pillars: the technological development of economies and the specifically oriented efforts of countries seeking to reduce trade barriers, especially non-tariff barriers. Obviously, especially following the nationalist and tariff-based policy of the Trump era, this trend, regrettably, does not remain empirically true, to the detriment of all. Trade facilitation gains substance and prominence throughout this process of reduction of barriers. Customs administrations, in this scenario, are identified as protagonists, implementing actions to strengthen and secure the entire process of entry and exit of goods from national territory, while at the same time contributing to socioeconomic growth through revenue collection and trade facilitation.

In this context, the main challenges of the customs administration may be identified as: (i) efficiency and operational excellence, directly related to investments in technology for the automated processing of transactions; (ii) the enactment and implementation of effective measures aimed at reducing bureaucracy in processes and lowering costs, streamlining transactions and making them more attractive; and (iii) the maintenance of security and process compliance, through the implementation of appropriate international risk management procedures, which tend to allow control of these relations to focus on cases that may truly harm international trade.

It must be emphasised that customs control is not an end in itself but a means of securing the best possible realisation of the national interest. Customs must be sufficiently streamlined and agile to ‘facilitate trade’ and not function as an obstacle to economic development, while at the same time ensuring an effective exercise of customs police power capable of detecting tax evasion and preventing, for example, the entry of prohibited imported goods.

In a globalised world, above all, it is necessary to be ‘light’ and to be ‘prepared’ for healthy integration. In modernity, in homage to the primacy that must be accorded to the national interest guiding the entire customs administration, Customs is tasked with safeguarding national development and with best meeting the needs of the country. In this vein, the challenge lies in unlocking the gates and knowing how to guard them not merely as a sentinel, but also as an agent that induces national development.

5. Specific principles of a customs tax law

In addition to qualified and specific principles of customs law, as already discussed, customs matters ‘contaminate’, to some extent, tax law. In this sense, there are certain principles of tax law that are forged within customs law and that apply exclusively to taxes levied on import and export transactions.

It should be emphasised that customs authorities are largely responsible for the collection of customs taxes proper, as well as of the so-called ‘equalising taxes’, which serve to homogenise the tax burden imposed on products circulating in the domestic market with that imposed on imported products. Likewise, the same tax on the circulation of goods and services (Imposto sobre Circulação de Mercadorias e Serviços, ICMS) applicable to transactions occurring in domestic trade could, were it not for the immunity provided for in art. 155(X)(a) of Brazil’s Federal Constitution of 1988 (Presidência da República, 1988), be levied on the export of commodities, as occurred before Constitutional Amendment No. 42/2003 (Presidência da República, 2003).

For this reason, it is necessary to investigate whether there exists, for example, a ‘tax-customs principle of non-taxation of exports’, or the ‘most-favoured-nation (MFN) principle’, or even the ‘principle of the national territory’.

The Federal Constitution of 1988 establishes the guarantee of national development as one of the fundamental objectives of the Federative Republic of Brazil (Presidência da República, 1988). In the field of exports, this objective may be pursued through taxation at destination. The competitiveness of Brazilian products in the international market largely depends on this tax relief of exports.

The destination principle of international trade enters the Brazilian legal order through the immunities applicable to transactions that direct goods and services abroad, including the tax on industrialised products (Imposto sobre Produtos Industrializados, IPI), ICMS and the tax on services (Imposto sobre Serviços, ISS), as well as social contributions and contributions for intervention in the economic domain levied on export revenues. It is also reflected in the constitutional requirement that corresponding taxes be levied on imported goods or services (Presidência da República, 1988).

Thus, the principle of taxation at destination adopted in international trade was incorporated into the legal order by the Federal Constitution of 1988, in the form of a ‘(sub)legal principle of the non-exportation of taxes’, as recognised by the Federal Supreme Court (Supremo Tribunal Federal, STF) in RE No. 474.132/SC (Supremo Tribunal Federal, 2010) and RE No. 606.107/RS (Supremo Tribunal Federal, 2013). However, as is well known, not all the tax burden is capable of being fully removed from exported goods and services.

It was for this reason that, in 2011, the federal government, with the aim of not impairing the export of national products through taxation and, above all, in strict compliance with the constitutional immunity of exports, created the Special Regime for the Reinstatement of Tax Values for Exporting Companies (Reintegra) (Presidência da República, 2011). By giving practical effect to the constitutional mandate, the legislation states that Reintegra aims to ‘reintegrate amounts related to residual federal tax costs existing in their production chains’ and permits the partial or full refund of the federal tax residue remaining in the production chain (Presidência da República, 2011, arts. 1–2). In theory, export production chains may be relieved through the application of the technique of ‘non-cumulativity’, by means of which it is possible to identify which tax was paid at each stage of production and to pass it on to the final consumer. By immunising exports and guaranteeing the right to input tax credits, exports would be relieved of taxation. However, as is widely known, even for the ICMS the system is not perfect, and the price of products destined for export ends up being ‘contaminated’ by so-called tax residues.

The deficient ‘non-cumulativity’ of the Social Integration Program (Programa de Integração Social, PIS) contribution and the Contribution for the Financing of Social Security (Contribuição para o Financiamento da Seguridade Social, Cofins), is neither a benefit nor absolute. It is a ‘technique’ that must be given density through infraconstitutional legal rules. PIS/Cofins input tax credits do not ensure tax neutrality nor the shifting of the tax burden; they merely serve to reduce the overall taxation along the production chain. Unlike a (perfect) ‘tax-against-tax’ credit system, in which the tax previously paid is offset and the tax burden is passed along, in the case of PIS/Cofins the crediting mechanism simply and solely promotes a reduction of the total tax burden throughout the production chain. By virtue of the very structure of the crediting system of these contributions, it is impossible to purport to neutralise the cascading taxation that occurs along the production/services chain.

Reintegra, in this vein, is merely a complementary procedure to the constitutional technique of non-cumulativity, supplementing it to apply and give density to the ‘purported’ constitutional (sub)principle of the non-exportation of taxes. For this reason, it does not constitute a ‘benefit’, but rather a right of the exporter to recover tax costs incurred at links of the production chain that burden exports. The complementary mechanism thus serves to enable the effective immunity of exports by relieving residual burdens caused by cumulative taxes. This is the understanding that ensures a higher level of effectiveness for the constitutional norms that exempt exports and, thereby, seek to enhance the competitiveness of national industry.

The immunities applicable to Brazilian exports derive from constitutional norms that are simultaneously programmatic and policy-inducing, and which, as a state public policy, should not be left at the mercy of the convenience or revenue needs of governments. The harm to the national economy resulting from the loss of competitiveness of national products in foreign markets is incalculable and, manifestly, flagrantly contrary to the objectives enshrined in the Brazilian Constitution, especially the fundamental objective of promoting ‘national development’. In furtherance of momentary treasury revenue interests, the private interests of national taxpayers cannot, evidently, be sacrificed, under penalty of offending the overarching fundamental objective of promoting economic development (and defending the ‘national interest’).

Regarding the most-favoured-nation (MFN) principle, set forth in Article I:1 of the GATT, each signatory country undertakes to grant to all other contracting parties, immediately and unconditionally, any relevant advantage accorded to the product of another country (WTO, 1947). This ensures that none of the contracting parties may enjoy more favourable treatment to the detriment of the others. In turn, the national treatment principle in Article III:4 of the GATT provides that imported products ‘shall be accorded treatment no less favourable than that accorded to like products of national origin’ (WTO, 1947). This prohibits discriminatory favouritism with respect to internal regulation and taxation based on the origin of the goods.

The two principles of customs law forged within the GATT operate as true limits on the incidence of internal taxes, affecting the power to ‘establish’ taxes and decisively ‘irritating’ tax law. They are not limited to affecting tax incidence on importation and exportation, insofar as they may also translate into limitations on the very incidence of internal taxes that would allow favourable treatment of national products. In this sense, principles of customs law that do not refer solely to taxation, but have a broader scope, end up affecting the power to tax, thus assuming a certain ‘customs-tax’ character. These are principles proper to customs law, broader in reach, which affect the power to tax and bind both the legislator and those applying tax law.

Thus, customs principles are revealed that, although intrinsically related to customs law, combine within their structure a fiscal and revenue-oriented dimension. More precisely, because they affect the fundamental structure of tax law, reaching the very ‘establishment’ of taxes, they are characterised as principles proper to customs tax law.

6. Conclusion

In conclusion:

  • Customs law governs legal institutions that are proper to its normative field. These institutions are specific to customs relations and have received autonomous doctrinal treatment within the legal discipline.

  • Customs law has a multifaceted structure because it regulates institutions associated with public law and institutions associated with private law. This feature does not compromise its autonomy. It confirms that customs relations are formed through the interaction of different legal categories under a specific normative arrangement.

  • Customs public administrations must pursue the national interest. This interest requires administrative action directed to the common good of the nation-state, as legally defined and implemented through the competences conferred upon customs authorities.

  • The national interest has a composite legal structure. Customs administration is required to safeguard a diversified set of public interests, which may be misaligned in concrete situations. Customs law must therefore be guided by the satisfaction of the national interest, understood as the legally ordered composition of those interests.

  • The national public interest operates as a dynamic equilibrium among public interests that may conflict in concrete cases. In the formation of the national interest, the private interests of nationals cannot be categorically excluded as interests opposed to the public interest. The national interest is therefore the legally structured synthesis of public interests and the private interests of nationals.

  • The overarching guiding norm of customs law is the principle of the supremacy of the national interest. Its scope is comprehensive because the interest protected by customs law is itself composite and relates to the legal position of the nation-state in international trade, border control and customs enforcement.

  • Customs authorities cannot act arbitrarily. The application of the principle of the supremacy of the national interest must be compatible with legal certainty for regulated parties. Customs law must discipline the national interest while preserving the legal security owed to private parties.

  • The application of the national interest does not authorise a generic or inherent state power of action. Such a power is incompatible with a rule of law under legality. Customs law develops through the defence of the national interest within the limits established by law and subject to proportionality.

  • The power of action attributed to Customs has an instrumental legal nature. It supports state action aimed at realising the national interest. The primary purpose of Customs should therefore not be reduced to control, since control is legally justified by the need to allow Customs to act in furtherance of national interests and within the limits of its statutory competences.

  • Several international treaties of the 20th and 21st centuries were concluded to promote trade facilitation. These instruments seek to stimulate national economic development and to protect the national interest of their signatories through rules directed at the simplification, transparency and rationalisation of customs procedures.

  • Customs control is a means for securing the best possible legal application of the national interest. Customs must be sufficiently agile and streamlined to facilitate trade and avoid obstructing economic development. At the same time, it must preserve effective customs police power to detect tax evasion and prevent the entry of prohibited imported goods.

  • Certain principles of tax law are formed within customs law and apply specifically to taxes levied on import and export transactions. This is the case of the subprinciple of the non-exportation of taxes. Even so, the fundamental guiding norm of customs tax law remains the principle of the supremacy of the national interest, which operates in concrete cases with broader normative reach.

  • The MFN principle and the national treatment principle operate as limits on the incidence of internal taxes and affect the power to establish taxes. These are principles of customs law with a scope broader than taxation, although they affect the taxing power. Customs principles may therefore reach the fundamental structure of tax law, including the establishment of taxes, and may be characterised as principles proper to customs tax law.