> 1) the chief patrol agent has to set the distance to encompass an inappropriately large area in violation of this law,

Certain to happen.

> 2) an agent has to stop and search cars randomly,

Not at all. "Based on my training and experience, Mexicans drive Subarus. Your driving a Subaru gives me a reasonable suspicion to conduct a non-random stop on you.". Yes, it gets very close to that stupid, and a lot of times they even believe stuff like that. Even if they don't believe it, they know the lie isn't falsifiable. A system that lets random officers get away with unreviewed searches is a problem even if they do have to commit perjury to take advantage of it. Because they will.

> 3) somehow become suspicious that an occupant is seeking entry and ought to be denied entry,

Well, yeah, they're sitting right there in the freaking Subaru. Boom. Reasonable suspicion.

> 4) believe that searching that person's device would reveal information demonstrating that the suspicion is correct.

Well, if the suspicion were correct, it probably would. And if the suspicion is incorrect, even if the suspicion is a deliberate bullshit lie, anything they do find becomes fair game.

Sorry, no. Probable cause. And independent judicial review on your probable cause. Not trivial legitimization of totall bullshit suspicions.