The Lwów New Union Treaty of 1991 was the treaty which transformed the Soviet Union from a single-party communist dictatorship to a multiparty, western-democracy.
The treaty was signed in Lwów in order of the new nationalities policy which was approved on December 1990, this police included that all the territories that were taken from Poland between 1939-1945 will be declared as "Polish Nationality Territory" which meant that Polish language will be official in the republics of Ukraine, Belarus, and Lithuania, and will no longer be an official minority language. Polish language will be used to educate people in this areas for transform them in Polish-speaking areas as they were before 1939. Another policies added to that treaty was that any republic could secede from the Union freely, without any conditions if the majority of that republic wanted, and, the reapplication of the Koreznitsaya policy initiated by Lenin and used during the early years of Stalin government.
The treaty also transformed the highly centralized Soviet Union into the decentralized confederation Sovereign Union.