Drug scanner checks public

They were not tested positive for drugs. They were tested positive for having been near them, not illegal in any way even in the UK... yet.

You are right... people complied. I wonder what would have happened if someone had said what they should have "fuck you, I'm going in without you sniffing me, shove that thing up your ass"?

They are allowed to test drivers but not pedestrians unless they break a law.
Driving is a privilege, walking is a right. Cops cannot interfere with just anyone because they feel like it and never should be able to.