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.