It's complicated. See Patriation for explanations:

Patriation was the political process that led to full Canadian sovereignty, culminating with the Constitution Act, 1982. That Act was necessary because after the Statute of Westminster, 1931, Canada decided to allow the British parliament temporarily to retain the power to amend Canada's constitution with the consent of the Canadian government. That authority was removed from the UK by the passing of the Canada Act, 1982 on March 29, 1982, by the Parliament of the United Kingdom, as requested by the Parliament of Canada.

Patriation was subsequently confirmed by Canada's Constitution Act, 1982 which was signed by then Prime Minister Pierre Trudeau and by Elizabeth II as Queen of Canada on April 17, 1982 on Parliament Hill in Ottawa. Queen Elizabeth's constitutional powers over Canada were not affected by the Act. She remained monarch and Head of State of Canada, separate from her role as the British monarch or the monarch of any of the other Commonwealth realms. Canada has complete sovereignty as an independent country, however, and the Queen's role as monarch of Canada is separate from her role as the British monarch or the monarch of any of the other Commonwealth realms.