JeffT, I see you live in Calgary as well. I can tell you for certain that IS illegal to keep ANY native species in Alberta. No garters, no hoggies, no black racers, none of them. Call Fish & Wildlife and report him. He'll get a nasty fine, and the snake will be released as soon as it is safe to do so.
Failing that, slap the care sheet on him.
Failing that, just slap him. Repeatedly.
- Ken LePage