This doesn't sound legal, but maybe I'm wrong:

My wife went to get new tires at tire chain. We told what kind of car we had and they said they had the correct size. The old tires were removed and then they apperently found the size they had was wrong. When she asked them to just put the old ones on for now, they said that they couldn't, that it was "illegal" for them to put tires that showed exessive wear. Basically the only choice was to buy other tires, or have a car that is not drivable!
does that sound right?

I've hear simmilar stories about this " cant put your old tires back on". Usually it's more like this:

you removed your all season prior to the winter and put on snow tires. now it's spring and you go somewhere to switch out the snow tires. The shop removes the snow tires, but then says that they cannot legally put on the all seasons back bc they don't have enough tread life left, and that it would be "illegal" for them to do so and they would be held liabel.

Your choice now is:
1.)buy new all season
2.)put the snow tires back on

otherwise the car is undrivable with no tires.

this does not seem legal. is it?

This happened with my wife more than two years ago, and I don't plan to do anything about it, but I've since heard about it happening again and wondered if it was just a way to railroad people into buying tires at whichever garage this happens in.

thank you for your help.