They could just as easily buy a car and cut it up. IP is generally protected by (threat of) a courtroom, not obscurity.
The high price of car parts is the reason why we have so much car theft. Promoting the availability of car parts will save costs for car insurance, law enforcement, the prosecutors, judges, juries, and jails.
The situation is outrageous. There are parts for which a dealer pays around $10.00 that retail over $500.00.