What document played a key role in establishing Canada as a self-governing dominion within the British Empire?

The British North America Act of 1867 is significant because it marked the beginning of Canada’s journey towards self-governance by creating the Dominion of Canada. This act united the provinces of Ontario, Quebec, New Brunswick, and Nova Scotia into one federation, providing a framework for governance and establishing a parliamentary system that was modeled after that of the United Kingdom. It also detailed the powers of both the federal and provincial governments, setting the stage for Canada to function with a degree of autonomy while still being part of the British Empire.

This act is a foundational legal document in Canadian history, as it not only created a new country but also laid out the conditions for its governance, which would evolve over time. Other options, while important in their own contexts, do not directly reflect the same foundational governance aspect in establishing Canada as a self-governing entity within the British Empire. For instance, the Canadian Constitution encapsulated various laws and amendments enacted later, while the Statute of Westminster furthered legislative independence earned afterCanada's initial establishment. The Magna Carta, though a historic document for the establishment of legal rights and liberties, is not specifically related to Canada’s formation.