The three Baltic countries, or the Baltic states – Estonia, Latvia, and Lithuania – are held to have continued as independent states under international law while under Soviet occupation from 1940 to 1991, as well as during the German occupation in 1941–1944/1945. The prevailing opinion accepts the Baltic thesis that the Soviet occupation was illegal, and all actions of the Soviet Union related to the occupation are regarded as contrary to international law in general and to the bilateral treaties between the USSR and the three Baltic countries in particular.
This legal continuity has been recognised by most Western powers and is reflected in their state practice. The application of the Stimson Doctrine by the Welles Declaration where a significant segment of the international community refused to grant formal approval for the 1940 Soviet conquest during World War II, the resistance by the Baltic peoples to the Soviet regime, and the uninterrupted functioning of rudimentary state organs in exile support the legal position that sovereign title never passed to the Soviet Union, which implied that occupation sui generis (German: Annexionsbesetzung, lit. 'annexation occupation') lasted until the Soviet Union recognized the independence of the three countries in 1991. Thus the Baltic states continued to exist as subjects of international law. On that basis, the Baltic states maintained that they did not need to follow the process of secession outlined in the Soviet Constitution, since they were reasserting an independence that still existed.