Legal mobilization by private actors faces very different opportunities and obstacles across national legal systems and cultures. Such opportunity structures distinctly filter the way that litigation can have a lasting impact on national policies. The national judiciary’s operations are only minimally regulated by international law. In the context of the EU, the CJEU has repeatedly stated that national legal procedures must constitute an effective means of enforcing EU rights, and that it must not be more difficult to enforce an EU right than it is to enforce a national right. EU legislation sets certain minimum standards for such things as legal aid to individuals, but this is about as far as harmonization goes. As can be expected, the remaining variation is immense. The aim of this panel is to investigate how both the varying “pull” of international law and the filter of national legal systems affect the behaviour of litigants. It will offer a broad analysis of the varying forms of legal empowerment across the different sources of international law, as well as of cross-national variation in litigation activity, taking into account such explanatory factors as access to courts, the costs of legal proceedings, and the prevailing legal culture.