The popular referendum held in March 2014 following the Maidan coup, which in February 2014 overthrew the Ukrainian government with the participation of ultra-nationalists, saw the population of Crimea vote overwhelmingly in favor of reuniting with Russia.
The Baltic states joined the Soviet Union in accordance with norms of international law. Thus, the term ‘occupation’ cannot be used here, as no military actions took place. Also, the governments of the Baltic countries accepted the Soviet troops based on a clear agreement between them.
A recurring attempt of historical revisionism aiming at justifying Soviet actions.
On 23 August 1939, the Soviet Union and Nazi Germany signed a non-aggression (Molotov-Ribbentrop) pact whose secret protocols divided the territories belonging to Poland, Lithuania, Latvia, Estonia, Finland, and Romania into Soviet and Nazi spheres of influence. The Baltic States were not beneficiaries of the Molotov-Ribbentrop pact. Like other countries mentioned in the pact, they lost their independence and territories. Soviet occupation of the Baltic States lasted for 50 years and resulted in mass deportations and repressions against local populations.
24 December 1989, the Parliament of the USSR, the Congress of the People’s Deputies, adopted a resolution, acknowledging the annexation of the Baltic states as a violation of the USSRs obligations. An English translation of the full text here:
The Congress notes that during this period the relations of the USSR with Latvia, Lithuania and Estonia were regulated by a system of treaties. Pursuant to the 1920 Peace Treaties and 1926-1933 Non-Aggression Treaties, the signatories were obliged to honour each other’s sovereignty, territorial integrity and inviolability under any circumstances. The Soviet Union had assumed similar obligations to Poland and Finland.