In Arizona v. Gant, by a 5/4 decision, the Supreme Court largely reversed New York v. Belton, which had said that a police officer could search a car when they arrested someone without probable cause.

It was an odd mix of judges too who voted in favor of the 4th amendment, Stevens, Souter,Ginsburg, Scalia(!) and Thomas (!!!).

Basically, the old rule was that if you arrested someone, you could search his car, and now the standard is, “police may search a vehicle without a warrant only when the suspect could reach for a weapon or try to destroy evidence, or when it is ‘reasonable to believe’ there is evidence in the car supporting the crime at hand.”

The other 4, including the 2GW Bush appointees, think that it will be too confusing, but it’s not: If you arrest someone for an expired license, or not seat belting their kids, and they are away from the car, you do not have authority to search it.

This ain’t rocket science.^*

^*Full Disclosure, in 1999-2000 and 1996-1998, I worked as a mechanical engineer for what is now Lockheed Martin Missiles and Fire Control, and I have some claim to actually having been a rocket scientist.