Most of the provisions of C-6 have that "Governor in Council" clause who determines the date that the new regulations come into force (same for 3/5, language requirements and so on".
About your question "Who is the Governor in Council and how does the process work":
Short answer:
The responsible Minister (in this case: Ahmed Hussein) decides on a date, based on feedback by their staff. It then gets published in the Canada Gazette. That's the date.
Long answer for those of you who are interested in the Canadian Constitutional Framework:
The
Governor General, as representative of Her Majesty the Queen, sets the date, because all executive power is vested in the Crown. However he does so "in council" which means that according to constituional convention, the Monarch or her representative doesn't decide alone but acts only on the formal advice of the "Queen's Privy
Council for Canada" which consists of the current government as well as many other dignitaries (former Prime Ministers, some former MPs, other honoured people, even Prince Charles sits in that one). However, again by constitutional convention, the Monarch (and, by extension, the Governor General) is only advised by those privy councillors that are currently in the Cabinet. The Cabinet consists of the current government of Canada, that is the Prime Minister and the other Ministers of the Crown. Within the Cabinet, again by convention, every Minister is responsible for the laws concerning his subject area. In this case Ahmed Hussein, the Minister for Immigration, Refugees and Citizenship is the responsible Minister.
So if you walk that chain backwards:
- IRCC employees will discuss with the Minister what a good date is
- It is possible that Justin Trudeau and/or his staff also has a say in this and joins the conversation
- The Minister will then advise the Governor-General of the intended date
- Since the Minister is the person responsible for this matter in the Cabinet which is the deciding body of the Privy Council which is the advising body of the Monarch, this is a binding advice that the Governor-General must follow
- The Governor General then proclaims the date in the Canada Gazette, starting with the following enactment clause "Whereas [insert references to law here] ... Therefore, His Excellency the Governor General in Council, on the recommendation of the Minister of Refugees, Immigration and Citizenship, decides that..."
And if you wonder "Why is this so convoluted, why can't it just say the Minister decides": Welcome to a Commonwealth Realm which has to carry centuries of constitutional baggage originating in some random fight Kind so and so had with Lord so and so over whatever.