There exists a range of situations where non-state actors and states can possibly share responsibility for their contribution to harmful outcomes, thereby raising a multitude of questions on the determination, content and implementation of responsibility in such a scenario. It may be tempting to adopt an approach whereby a shared responsibility regime involving non-state actors and states draws ex post on the regime put in place by the ILC Articles on Responsibility of States for Internationally Wrongful Acts, especially in connection to the rules of attribution of conduct and attribution of responsibility. Such a model of international responsibility, however, would only work to the extent that addressees are bound by primary norms of international law in the first place. This is certainly not a given in respect of non-state actors. Moreover, non-state actors may differ fundamentally from states, thereby making the transposition of traditional rules of state responsibility artificial and inadequate: their loosely organised, temporary, diverse, illegitimate, or even outright criminal character may militate against applying the classic responsibility paradigm to non-state-state interactions. In view of these limitations, a turn to an ex ante approach to questions of shared responsibility, through standard-setting, has been suggested, and may be cautiously supported in respect of the activities of a number of non-state actors. This, however, is not exclusive to the simultaneous application of ex post and ex ante approaches to shared responsibility.