The International Association of Democratic Lawyers (IADL), founded in Paris in 1946 by a group of antifascist lawyers, has long been dismissed as a Soviet front organization. Yet, this characterization overlooks its complex and multifaceted history. This paper reassesses IADL’s first thirty years, exploring its origins, internal debates, and cross-border engagement. Drawing on archival records, this article argues that—despite a period of Communist influence—the IADL contributed to international legal and political discourse by advancing an original approach defined here as radical legal internationalism. Through this framework, IADL lawyers questioned Cold War ideological boundaries and brought into dialogue Communist, progressive, New Left, decolonial, and liberal rights traditions. The article also uncovers the IADL’s significant role in promoting international law and human rights through trial observation, UN advocacy, and missions of inquiry. In challenging the dominant account of the Left’s delayed and uneasy embrace of human rights, this article calls for a broader understanding of Cold War-era legal internationalism and highlights an alternative tradition of legal activism.