A humane way I've found with rats (or similar animals such as voles) is to set up a live trap. Check it once in the morning and once at night. After you catch them, release them far away from your house in the middle of woods or something so they find a new home far away from you. Keep the trap up until no rats have been trapped for a few weeks. Then you should be good. Sorry, I know nothing about Alberta but I would think it's legal.
The only illegal rat that I know of having is called a pouch rat. They are twice the size of a normal rat. One was imported in the United States and was infected and spread Monkeypox. So they banned importation of them in the United States. As for Canada I am not so sure.