Permissive Rules in Public International Law

The idea of permissive rules, i.e. legal rules permitting a certain course of action, seems problematic. Typically, one expects the legal order to prescribe a certain behaviour. Howev- er, on closer observation, several examples of permissive rules can be found in the (interna- tional) legal order. Notably, in the Lotus case, the Permanent Court of International Justice expressly referred to the concept of permissive rules. This gives rise to the question of the legal relevance of such permissive rules as well as of the specific function they fulfil in inter- national law. Yet, the phenomenon of permissive rules has hitherto not obtained the attention in the international law discourse which it would deserve. The main hypothesis of the proposed research project is that in order to properly understand contemporary international law, a distinction should be drawn between a thin and a thick concept of permissive rules. While the former version of permissive rules equals non- prohibition, the latter version means that someone is entitled or has the right under interna- tional law to follow a certain course of action. This distinction is relevant not only on the theo- retical level, since thin and thick permissions entail different legal consequences for the ac- tors involved. In particular, if an actor is permitted (i.e. not prohibited) to follow a course of action, this does not imply that other actors on the international plane are obliged to recog- nise this permission. In contrast, a thick permission creates duties for other actors. In the framework of the project, on the basis of a tentative definition of permissive rules, a sample of 50-60 multilateral treaties (in their English, French and German versions) shall be analysed as to whether and to what extent they contain such permissive rules. Subsequently, the main hypothesis of the research project shall be tested against the identified instances of permissive rules. It will notably be examined where examples for both the thin and the thick concept of permissive rules can be found in international law and whether the legal conse- quences entailed by them are compatible with what the hypothesis suggests in this regard. To that effect, three fields are tentatively identified which appear as particularly promising candidates for exploring whether the distinction of a thin and thick concept of permissive rules is safely grounded in the contemporary international legal order, namely the law of se- cession and self-determination, international humanitarian law (in particular the purported right to kill enemy combatants) and the international law of sanctions. The project shall be conducted by Assistant Professor Dr. Andreas Th. Müller, Department of European Law and Public International Law, University of Innsbruck, as project leader as well as two PhD candidates.

The idea of permissive rules (Erlaubnisnormen), i.e. legal rules permitting certain actions, is all but self-evident. Law is typically portrayed as a system of rules controlling human behavior by (positively) ordering or (negatively) prohibiting certain actions. However, at closer observation it becomes manifest that permissive rules are commonly utilized in legal systems, including international law. Nonetheless, the permissive rules concept has hitherto not obtained the attention it deserves in international law scholarship. The research project proceeds from the hypothesis that a distinction should be drawn between a thin (weak) and a thick (strong) concept of permissive rules. While the former refers to a situation of mere non-prohibition, the latter describes an actors actual entitlement or right to display a certain kind of conduct. This is not merely a conceptual difference, but has identifiable legal consequences. A permission in the sense of a non-prohibition, i.e. a thin/weak permissive rule, does not entail obligations for other actors on the international plane. In contrast, a thick/strong permissive rule, by virtue of bestowing entitlements and rights on one actor, creates corresponding duties for third actors. In the first phase of the research project, the theoretical background of the permissive rules concept was examined based on Wesley N. Hohfelds scholarly works. In addition, the PI and his research team screened a sample of about 40 multilateral treaties in their authentic English and French language versions in order to find concrete examples of both thin and thick permissive rules. On this basis, the research team could identify the following areas as the most promising for further research: 1) self- determination and secession; 2) international humanitarian law, notably the killing of enemy combatants; 3) espionage; 4) air defense identification zones; 5) unfriendly acts and retorsion. The research conducted in the framework of the project has confirmed the initial hypothesis that the permissive rules concept may serve as a useful instrument to conceptualize phenomena in international law that fall into grey areas and therefore resist to be easily classified into standard accounts of international law. The permissive rules concept has already been successfully applied to the field of self-determination and secession where the PI published an article in a renowned international law journal. In addition, the PI and a project staff member are co-authorizing a journal article addressing the phenomenon of espionage in a permissive rules perspective. In addition, the staff member in question works on a PhD project comprehensively examining the phenomena of unfriendly acts and retorsion, including in a permissive rules perspective. Furthermore, the research project was presented by the PI to, and discussed with, peers at the Universities of Frankfurt a.M. and Zürich as well as at the University of Michigan Law School.