Introduction
What determines the relationship between constitutional law and international treaties, and what role do courts play in shaping this relationship? The literature oscillates between cultural and institutional explanations.
Cultural explanations pertain to the legal and political culture of a country, whether it has a tradition of nationalism or internationalism, a culture of cooperation or not,1 and whether it is international or the domestic law that is seen as the ‘original’ legal order from which the other derives.2 Institutional explanations draw upon factors such as the ‘flexibility’ and the degree of detail in a constitution and - closely related - the role of judicial review.3 The easier a constitution can be amended and the more difficult it is for courts to review the constitutionality of treaties, the more it becomes necessary to grant primacy to international treaty law (even over the1 See D Thurnherr, ‘The Reception Process in Austria and Switzerland’ in Helen Keller and Alec Stone Sweet (eds), A Europe of Rights: The Impact of the ECHR on National Legal Systems (Oxford, Oxford University Press, 2012), 335 for such a cultural explanation. She is of the opinion that the incorporation of the ECHR was swifter in the francophone Cantons of Switzerland as compared to the German speaking Cantons due to the ‘more cosmopolitan attitude’ of the former. See also R Wahl, ‘Das Bun- desverfassungsgericht im europaischen und internationalen Umfeld’ in Robert C van Ooyen and Martin H W Mollers (eds), Handbuch Bundesverfassungsgericht im poli- tischen System, 2. Aufl. (Wiesbaden, Springer VS, 2015), 831.
2 S Hobe and O Kimminich, Einfuhrung in das Volkerrecht, 10th edn (Tubingen, Francke, 2014), 240; A Verdross and B Simma, Universelles Volkerrecht: Theorie und Praxis, Unveranderter Nachdruck der 3. vollig neu uberarbeiteten Aufl.
von 1984 (Berlin, Duncker & Humblot, 2010), 54.3 See M Schlogl, ‘Strategen in Roben: Einflussfaktoren auf die Rechtsprechung des U.S. Supreme Court und deren Implikation fur das Bundesverfassungsgericht’ in Robert C van Ooyen and Martin H W Mollers (eds), Handbuch Bundesverfassungsgericht im politischen System, 2. Aufl. (Wiesbaden, Springer VS, 2015), 897. Overall, see also L Epstein and J Knight, ‘The Economic Analysis of Judicial Behavior’ in Lee Epstein, Stefanie A Lindquist and Jack Knight (eds), The Oxford Handbook of U.S. Judicial Behavior (Oxford University Press, 2017).
DOI: 10.4324/9781003200666-4 constitution) since this is the only way to entrench its binding character.[65] The common denominator of these factors is that they shape the extent of the ‘friction surface’, the potential of real conflict between international and constitutional law.
The concept of a ‘friction surface’ that I would like to introduce in this chapter is aware that a pyramidal concept of law, where international public law sits on top, with national constitutional law as a second layer and national statutory law as a third layer, etc., is overly simplistic.[66] It cannot account for the degree to which international law is self-executing and it cannot distinguish between a supremacy within the realm of international law and a possibly differing rank of legal norms in the realm of domestic law.[67] What is more, it cannot account for the fact that the risk of conflict between national and international law heavily depends on the degree to which different countries are involved in international cooperation and namely whether they are member states of supranational organisations or not. Finally, it cannot distinguish between supremacy of one legal order over the other in the application of law as opposed to the supremacy of norms as a constraint to law making. Nevertheless, national and international law create frictions with each other, both in the creation and in the application of law, between international law and constitutional law on the one hand and international law and statutory or lower ranking law on the other hand, and both with self-executing international norms and international norms in need of specification in domestic law.
This friction surface is hard to map or picture in a spatial way. It is much more complex than the imagined surface between two layers of a legal edifice.[68] However, if a multitude of factors is taken into account, its extent can be described, at least in relative terms, in the sense that it can be meaningfully compared to friction surface between another state's domestic law and international law. Thus, it helps to substantiate the analytical power of institutional explanations for the varying relationships of constitutional norms with international law in different countries.This chapter aims to add to such an institutional explanation. It argues that courts play an important role in shaping the relationship between constitutions and international law but that their role is structurally conditioned. The (growing) flexibility of a constitution is the main structural factor that courts must take into account when determining a constitution's rank with regard to international treaties. The easier it is to amend a constitution - and the more details it therefore contains - the larger the friction surface gets and the harder it becomes to avoid
Activism as defence 45 irresolvable conflicts with treaty law if - in the application to concrete cases - there is no supremacy of the latter over the former. In addition, the possibility of constitutional review is linked to the flexibility of the constitution and represents another structural factor for the role of courts. The pressure grows for an apex court to seek a ‘domestication of the supremacy of international law’,[69] i.e. to recognise a supremacy of treaty law not just in the international, but also in the domestic realm. For the domestic context, recognising the supremacy of international law over domestic law remains an exceptional practice (outside of the context of EU law). This holds true especially with regard to the supremacy of international law over the constitution.[70] However, the structural factors mentioned above nudge courts towards judicial activism to establish supremacy of international treaty law.
What is meant by judicial activism in the following is the willingness of courts to interfere with the decisions of other branches of government on the ground that those decisions allegedly are in conflict with higher-ranking law. Activism may also manifest itself in a procedural guise, namely, when issues are treated by a court, which are unnecessary to the disposition of the case.[71]
The case study I use to illustrate the influence of structural factors on apex courts is Switzerland, where a series of recent amendments to the constitution - in conflict with treaty law - has led to a jurisprudence that assures the primacy of (some) international treaty norms even over more recent constitutional norms. This, in turn, led to an initiative, which sought to amend the constitution anew in order to enforce the primacy of the constitution over international law,[72] a project that failed at the ballots in 2018.
I compare the case of Switzerland to Austria and Germany. These three mainly German-speaking countries share - especially in the field of constitutional law - a lot of common legal culture and common legal doctrine.[73] Yet, although all three of them are federal democracies, they differ starkly in terms of their institutional architecture regarding the role and the revision of their constitutions, the role of
constitutional review and their relationship to European and international law. These differences affect factors that determine the extent of the friction surface between treaties and the constitution.
Methodologically, this comparison follows the ‘most similar case’ principle:[74] it compares cases, which are similar in many aspects that are potentially decisive factors for the phenomenon under scrutiny, except for one of the possible explanations for the dependent variable.[75] The possible explanation that differs here is size of the friction surface between treaties and constitutions. The dependent variable is the rank of treaties relative to constitutions. The case selection should be helpful, therefore, to understand the role of institutional as opposed to cultural explanations of the role of international law in its relation to the constitution and for the role of top courts in shaping and developing this relation.
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