If two people are listed on teh title of a car, can one person sell it with out the permision of the other?

Answer 1

Nope

Answer 2

Not unless the second person is dead and even that is problematic as you couldn't sell it without having the deceased person's will probated (which could take years in some cases!).

The best course of action is to either "buy out" or "sell out to" the other partner or agree on a purchase price and other sale particulars, then sell the vehicle. The stories you hear every so often about the wife who co-owned her (ex-) husband's new Corvette, and sold it for a song are apocryphal at best.