An Act of the British parliament in 1791, altering the laws and governance of the British colonies in North America.
After the Treaty of Versailles (1783) ended the American Revolution, approximately 100,000 individuals loyal to the British Empire left the United States. Of these, about 40,000 to 50,000 settled in the British colonies to the north of the newly born United States. These people were collectively referred to as "United Empire Loyalists" or simply as Loyalists.
Of these about 30,000 settled in Nova Scotia, while the rest settled along the upper St. Lawrence river and along the shores of Lake Ontario and Lake Erie. These latter loyalists were not satisfied with the limited rights and French civil laws which existed in the province of Quebec. In order to allow these settlers to organize their own (more traditionally British) society, the Constitutional Act of 1791 was passed. It divided the British colony of Quebec at the Ottawa river, forming two provinces: Upper Canada and Lower Canada.
The act repealed potions of the Quebec Act of 1774. It gave both provinces an elected legislative assembly, something of a shock to the french population of the new Lower Canada, who had never had one before. These assemblies were given the right to levy taxes, which did little to endear them to the french speaking populace, especially as the power to spend the money so collected rested in the appointed Governor General and legislative councils of each province, and not in the assemblies themselves.
The Act also reaffirmed the people of Lower Canada's rights to the Roman Catholic Church and to French civil law (although the English criminal code prevailed throughout).