I am not saying that this was the case, but it could be that he is a federally funded state trooper. We have a couple of city, what we call clickit or ticket cops (seatbelt cops) that the feds pays their payroll, their duties are different from the others. We also have one dot that is funded by the feds, and I know the San Jon Scales in NM has a federally funded dot, their duties can be somewhat different too than the other dot's. The trooper could be something similar.
Make sure your brakes are adjusted BEFORE hitting the road. No OOS. Shouldn't even be an issue. MT has been known to check fuel. Bozeman.
I had fuel tanks inpected once around Nevada Mo. Drove by a white pu...mile later ,he drove up fast on me.Claimed he couldnt see my brake lights on tractor.I said, well.."Thats because I Wasnt using the Brakes ,sir". This was excuse to stop me."Ive been empowered by the State to inspect your fuel tanks for tax free off-road diesel" Showed an IRS card or whatnot.Had recent fuel receipt and everything to show.Ok,youre good to go...have a Nice Day..Lol