The Westminster system of cabinet government relies on the confidentiality of cabinet discussions, such that ministers can speak freely among their colleagues, and then they're bound by the decision that's called and bound by cabinet solidarity as a consequence of that. If you were operating in the open, like a city council, then people would behave like a city council and there would be far less candour within the cabinet room. That's the software on which Canada's federal and provincial governments run. It's been acknowledged as such by the Supreme Court.
That creates tensions between the different branches of government, and the courts will decide on that. The general framework has been set by the Supreme Court in more than one decision, and it's been set by the Federal Court in some specific cases in terms of arguments about specific documents and specific redactions.