The Oscar Chinn Case (United Kingdom v Belgium) is a seemingly petty case that raised fundamental legal issues and gave rise to deep divisions among the judges called upon to decide it. The majority judgment of 12 December 1934 remains important as a pronouncement, by the Permanent Court of International Justice (PCIJ), on the legality of regulatory interference in trade protected by international treaties. In addition, a brief statement by Judge Schücking has come to be seen as a precursor to modern debates about the ius cogens concept.2 In early 1929,