In the aftermath of the First World War, constitutions of European states were widely democratized and parliamentarized, and similar turns were expected in international relations as a consequence of the creation of the League of Nations. This comparative analysis of Swedish and Finnish parliamentary debates on the League membership focusing on conceptualizations of the national versus international demonstrates how democratization and internationalization merged discursively. This happened to a greater extent than in the British parliament or the First Assembly of the League. Such entanglements followed from the interconnectedness of constitutional and foreign policy questions during preceding disputes on constitutional reform when Britain and Germany had provided competing models, the determination of the ministries to reconfirm national constitutional compromises by joining an international organization of democratic nations, an exceptional possibility for parliamentarians to debate foreign policy and willingness among the leftist oppositions to extend the democratization and parliamentarization of the constitutions to the field of foreign policy. After a turn from German to British political models and under a Bolshevik threat, British internationalist arguments found a positive reception among the Swedish Liberal–Social Democratic coalition and the Finnish bourgeois coalition as well as half of the redefined Finnish Social Democratic Party. Rightist and far-leftist opponents of the League were left to the margins as the membership was used to redefine the polities as internationally oriented democracies.