How to get rid of car?

Question

how can someone legally get out of this situation- car is worth half what the loan is for and can no longer afford to make payments. if it is repo'd, would he get sued for the difference in $? can't sell because do not have the $ to pay off lien to get title.... any ideas?? will he have to go bankrupt? how could someone 'sell' him a car- give him a loan for twice the worth of the car anyway?