Law & Economics Working Papers
Erga omnes norms are those that give third-party states, rather than just the victim, legal claims against states that violate them. This paper argues that ordinary two-party norms arise when states recognize that a norm violation injures only one state and that other states that seek to retaliate on that state's behalf are likely using the violation as a pretext for predatory behavior. Erga omnes norms arise when states recognize that a norm violation injures multiple states and that states have an incentive to free ride rather than retaliate against the violator. Erga omnes norms reduce the incentive to free ride but at the same time reintroduce the risk that some states will use a norm violation as a pretext for engaging in predatory behavior.
Eric Posner, "Erga Omnes Norms, Institutionalization, and Constitutionalism in International Law" (John M. Olin Program in Law and Economics Working Paper No. 419, 2008).