The workshop unites research on the history of international law with studies on Eastern Eu-rope to investigate the controversial role of international law in the complex and conten-tious reordering of the region since the Congress of Vienna. The workshop proposes that the extraordinary density of political, social and ethnic conflicts and the decades-long struggles over territorial boundaries in Eastern Europe have left clear traces in international law. More specifically, the workshop addresses these issues through the lens of international institu-tions, which offer a starting point from which to identify topics; single out involved states, groups, and transnational actors from East Central and Eastern Europe; and reveal how re-gional constellations were universalized in the process of negotiating and implementing in-ternational norms and rules.