> To make a seizure all that is needed is reasonable cause that customs law/regs were violated.

What would be the reasonable suspicion that a USC bringing their personal phone on a trip with them would be a customs violation?

That doesn't sound at all reasonable.

In fact, the only "suspicion" they had was that he was someone who didn't like LE or Trump which is still not a crime, nor a customs violation.

No idea if its true, but one rumor mentioned was he was suspected of possessing CSAM