Erga Omnes Norms and the Enforcement of International Law

Abstract

Erga Omnes Norms and the Enforcement of International Law Comment by Alexander Stremitzer Introduction Under traditional “two-party” norms of international law, an aggression by state X against state Y only gives state Y the right to retaliate. If, however, a matter of international law is governed by “erga omnes” norms, all states are entitled to engage in countermeasures. This raises the question why some international legal norms have the status of erga omnes while others do not. Posner [2009] argues that erga omnes rules are likely to emerge in areas where, on average, externalities due to the original aggression are high, motives for taking norm violation as a pretext for engaging in predatory behaviour are weak, and incentives for free-riding are strong. Moreover, he predicts that erga omnes rules will reduce free-riding and hence increase the probability of enforcement. We shall argue herein that erga omnes rules can actually have the opposite effect of increasing free-riding and reducing the probability of enforcement. This might explain why genocide in Dafour is ongoing despite (or even because) being governed by an erga omnes norm. 2 Posner’s Analysis The basic tenet of Posner’s analysis is that, under perfect information, international norms emerge as equilibrium behaviour of states. 1 Consequently, violations only arise as the result of miscalculations, endgames and exogenous shocks on parties’ payoffs. Following this concept he argues that, absent externalities, erga omnes rules cannot arise in international law as they will never emerge as states’ equilibrium behaviour. Consider the obligation to respect the border of neighbours and assume that state X violates this norm and attacks state Y . If state Z subsequently attacks state X the question arises whether state Z can credibly claim that it only retaliates against the original aggression. The answer is no, as Z was not affected by the aggression. Therefore, X must conclude that Z’s action was purely predatory and thus constitutes a second This view is provocative in itself as many scholars of international law consider “opinio iuris”, i.e. the view held by states that they follow a norm out of legal obligation, to be an essential feature of law (see e.g. Roberts [2001]). ⇐=Au.: “Dafur” is now “Dafour”. O.K.?