It's not illegal in Canada
Actually, this is a very important point you got wrong. It is, in fact, illegal in Canada; the Canadian law is merely not enforced.
The US-Canada extradition treaty specifies that the US can only demand extradition in cases where the act was, by Canadian law, punishable by a prison sentence exceeding 1 year. Emery could only be extradited because Canada left that law on its books, even though it didn't actually enforce it.
The Parliament of Canada could have, at any time, shut down the extradition effort by simply repealing the law in question, or reducing the maximum sentence to less than a year, or the like. And despite the Conservative government, the House of Commons of Canada had a Liberal-NDP-BQ majority during most of the extradition effort.
So Mr. Emery is in jail because the freely-elected representatives of the Canadian commons, of all parties, jointly exercised the sovereign power of the Queen-in-Parliament to outlaw his conduct under Canadian law and keep it illegal under Canadian law.