This whole thing highlights how insane US border law is.

Sam was physically in the US, but because he was on an international flight, he was arrested in a manner that would be unconstitutional anywhere else in the US. He was denied a lawyer, questioned for I presume hours, had his phone stolen without a warrant, and then was released because there was no crime CBP could figure out how to charge him with then and there.

Months later, he gets charged by a federal statute even though where he committed the crime was a place that federal law does? doesn't? extend. Apparently it's a very convenient place where the constitution is void but federal laws still matter.

Cops can't arrest or detain you without some articulable suspicion of a crime being committed. They can't steal your stuff to try and find a crime you committed. They can't search your phone without a warrant in which they provide a judge with enough evidence to reasonably suspect a crime has been committed.

Yet Sam apparently had no rights because he was put on a watchlist for exercising first amendment rights.

Very despicable behavior by the government and the federal prosecutors pursuing this case.

Indeed. Hopefully the next administration will hold current officials accountable for such abuses of power.