Your fourth amendment rights do not fully apply to cars. Why? Because a car is not a private place, it's one that's used on public roads in full view of everyone else. As a result, your right to illegal search and seizure only applies to your trunk and your glove box. Sure, you can refuse to pop your hood or your trunk, and refuse to get out of the car. But, if they find any reason that your car is not legal, like, say, an illegal exhaust, they can impound your vehicle. And this is perfectly legal.