Can a car dealer hold on to your plates if you owe him money for a warranty?

Other answer:

I would say the debt is a civil matter. Removing plates and holding them for "ransom" might be a criminal matter. If this is warranty work, why would anyone have to pay the repairman? If money is owed, the repair facility can place a mechanic's lien on the car (in reality, it's an artisan's lien). If the lien is not paid, then the mechanic can sell the car for what is owed. the repair facility should secure the car so that the owner can't come late in the evening with a 2nd set of keys and take the car (that would be a criminal act, also).
Car dealers in my state have nothing to do with plates except sometimes on brand new cars.

Cancel the warranty and get your plates.

how is it warranty if you owe for the work?
they will get their money, they have a mechanics lien on the car as soon as they work on it
Yep. They have lots of ways to get you to pay up. You better pay while they are still being nice about it.
From your question I'd say they DID.
Scott H:
Yes, as you probably already know.
Love big words:
sure nuff
Absolutely. They can, and they will.