"Sounds like legal problems for the states doing this. What is their probable cause for stopping them? For searching them? The fact that they are obeying the laws in their own state is not probable cause to assume they are criminals."
MB, if you're from Florida, let's say, and you're driving to Maine on vacation and you're stopped and harassed in NJ (i think it was), it's unlikely you'll go back to NJ to sue them. There are some who would, but after being worked over financially by those guys, most of us would just go home and lick our wounds. That's what they count on, anyway. That being said, the time to give them a hard time is when they ask permission to search and you say, "why certainly, officer, as soon as you show me your search warrant."
It's unbelievable how many idiots that are carrying contraband will actually consent to a search of their cars.