How do you get a car back from a friend who refuses to give up a car that is in your name?

IF the TITLE is in YOUR name as owner or co-owner, go get it. If you LOANED it to them, you might send a registered letter demanding they return the car and give "X" days to do so. Then you can report it stolen. They cant steal it as long as they have your permission to use it. Check with a local attorney or your DA for state specific advice.