This sort of thing is perfectly legal in Australia and New Zealand; it’s a Random Breath Test (although, as TheLoadedDog says, they’re always not as random as they like to make out). The cops can simply decide that they’re going to pull you over and breathalyse you for absolutely no reason. As long as you don’t blow over the limit, they generally wish you a safe evening and send you on your way.
I’m all in favour of this, but I will concede that RBTs are a slightly different kettle of fish than seatbelts, IMHO.
I got stopped on the interstate several years ago for no apparent reason. Cop came up to my window, and I respectfully asked what the problem was. Rather snarkily, he said, “No inspection sticker? No license plate?” Oh! I looked in the back window and saw that the paper new car dealer license had fallen off the back window. I stuck it back up. Oh.He examined the document carefully. “It expires next week.” “Yes, but it’s not expired now. We’re still waiting for the real ones from the DMV.” “Oh. All right then.” He checked all the paperwork, insurance card, license, etc. All my papers were in order. The officer was the very definition of “crestafallen.”
Dude if they want to pull you over, they just drive behind you and wait for you to violate some trivial element of the traffic code (changing lanes in an intersection, failure to signal or whatever) and hope they see something in car or in the way you’re acting to Terry frisk you. Because so-called “pretext stops” are perfectly legal as long as the thing they actually stopped you for is legitimate.