>You can write a law saying all vehicles need winterized tires during that time of year.

As a matter of fact, Quebec already has one[1].

>But how exactly would you enforce it?

The easiest way is probably similar to inspection sticker enforcement: by having the responding officer check the tires whenever a driver goes off the road, gets in an accident, or is otherwise pulled over. No winter tires? Enjoy a fat fine.

Will some drivers get away with it? Of course. You're never going to get 100% compliance. There are still people who live in states other than New Hampshire that still don't wear their seat belts.

[1]: https://www.quebec.ca/en/transports/traffic-road-safety/driv...