Canadians’ rights and freedoms are guaranteed by the distinction between Head of State and Head of Government in the Constitution Act (1867).
We have a backup system in the 1982 Charter of Rights and Freedoms. But without the 1867 Act our Charter rights would be pie in the sky, about as well grounded as wishes and dreams.
The Head-of-State/Head-of-Government system secures a populace from the depredations of ambitious political elites by providing for the orderly competition of political parties for office. (The assumption is that the greatest danger to citizens comes from would-be oligarchs.)
Think of Mr. Harper at the G20 meetings. For a happy day or two he was Mr. Canada. The Canadian political opposition was out in the streets, or sulking in Ottawa, and not in the G20 deliberating chamber. He was talking to kings and oligarchs as an equal. The posture was required by the occasion. But Harper knows, and we know, that no Canadian politician speaks for Canada in the way that King Abdullah speaks for Saudi Arabia or Putin, for Russia. It’s the Canadian Head of State, the Governor General, who speaks for Canada, that is, all of us. But the 1867 Act doesn’t allow a Governor General to govern. We don’t allow her to make policy.
Our political leaders are necessarily partisan; our governor general and constitution must be non-partisan. That’s the formula in the Constitution Act (1867). And that’s the formula for freedom in parliamentary systems: a Monarchic representative and a Prime Minister. “It takes two,” as the song goes.
Earlier this month an ad hoc group of academics, legislators, and journalists met in Ottawa to discuss “the purpose, functioning, advantages and drawbacks of the present system of constitutional monarchy in Canada.” They call themselves, Friends of the Canadian Crown. Among the sponsors were the Queen’s University Institute of Intergovernmental Relations and the Canadian Study of Parliament Group. Senators Serge Joyal and Hugh Segal officiated. I’d have liked to go; but one can’t do everything. The IIR will issue a book of essays on the subject sooner or later.
The Idea File 
An excellent defence of the Canadian Crown, Professor Ajzenstat, particularly your remark that
Here’s a perspective from another angle, that argues that the Crown, at least in theory, can act as a symbolic guarantor of limited government while, at the same time, serving as a model for the obligatory State.