Welles Declaration in the context of "Nazi-Soviet Pact"

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.

The Stimson Doctrine is the policy of nonrecognition of states created as a result of a war of aggression. The policy was implemented by the United States government, enunciated in a note of January 7, 1932, to the Empire of Japan and the Republic of China, of nonrecognition of international territorial changes imposed by force. The doctrine was an application of the principle of ex injuria jus non oritur. Since the entry into force of the United Nations Charter, international law scholars have argued that states are under a legal obligation not to recognize annexations as legitimate, but this view is controversial and not supported by consistent state practice.

Named after Henry L. Stimson, U.S. Secretary of State in the Herbert Hoover administration (1929–1933), the policy followed Japan's unilateral seizure of Manchuria in northeastern China following action by Japanese soldiers in Shenyang on September 18, 1931. The doctrine was also invoked by U.S. Undersecretary of State Sumner Welles in the Welles Declaration on July 23, 1940, which announced nonrecognition of the Soviet annexation and incorporation of the three Baltic states: Estonia, Latvia, and Lithuania. This remained the official U.S. position until the Baltic states regained independence in 1991.