You're speaking nonsense since there was no charge or warrant against him. People are free to use their phone for f sake.

Evidence exists independent of a charge or warrant. The instant they asked for access to the phone, it became evidence. If he had entered the duress code himself before walking up to the agent, he'd be fine. Nerds thinking that technicalities is how the law works is why he's in hot water.

Law enforcement doesn’t need a warrant to search phones at the border. I agree this is a terrible rule but it is the rule right now.

Have you read https://yalelawjournal.org/forum/customs-immigration-and-rig... ? Quoting from its abstract:

> While the Supreme Court has long recognized a border-search exception to the Fourth Amendment’s warrant requirement, it applies to only two interests: promoting the duty regime and preventing contraband from entering the country; and ensuring that individuals are legally admitted. The government’s recent use of the exception goes substantially beyond these matters.

None of these two interests apply to his targeted search. No duty applies here. By definition, no contraband can exist on an erased phone

Is that the 100 mile wide border?

You have lost track of the chain of discussion.