DUI checkpoints are specifically for checking for intoxication. I’m not a fan of them, but the ones I’ve gone through either asked me to blow, or asked me whether I had been drinking (cop sniffed the air) and didn’t do anything else. They didn’t go on a fishing expedition as to my itinerary for the next few weeks.

When you’re given a license, you sign an implied consent form allowing breath and drug testing. This does NOT extend to being required to state your personal business for the next few weeks.

BTW – the Border Patrol checkpoints don’t only necessarily check drivers. The 2-lane portion of Rt. 94 is theoretically usable by pedestrians and cyclists.