>Roadblocks still fall under regulations. For example, every third car.
Where in the world did you hear that?
Might want to take a look at
http://www.roadblock.org/ - I don't think (although I don't know for sure) that this is some type of regulation allowing them to stop on 1 out of every 3 cars. They can stop whoever for whatever - driving is not a right.
ICQ 10556 (ya), 254117