I love the spirit of what you’re saying, but per the attorney’s advice in this article, they might seize your phone no matter what you say, password protection with no fingerprint or face scan unlock should ideally keep them out (note that law enforcement usually can take your picture or finger print you without needing a warrant or anything, but they can’t force you to tell them a password), but you will probably never get that device back and you could be detained indefinitely while they try to intimidate you into waiving your 5th amendment silence rights.

So because citizens have an absolute right to reenter the country, they have a bit more leverage to, you know, deny a request or refuse to comply with requests to unlock their phone. But that doesn’t mean that there aren’t going to be consequences. They could be detained for several hours. Their phone could eventually be confiscated. So even U.S. citizens have to think about those potential consequences.

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[As for lawful permanent residents,] [t]echnically, they also have to be let back into the country, but as we’ve seen in sort of a nonborder contexts, the government and the current administration is pretty willing to question the status of LPRs. And so we always say that, you know, they should be especially kind of mindful and thoughtful about how they comport themselves at the border.

I think your best strategies would be 1) just do not travel to the United States if it can at all be avoided; 2) if you must to travel to the US, don’t bring any electronic devices capable of storing media with you, purchase new ones after you are past the border, securely download what you need, then erase and destroy those devices before leaving; 3) if purchasing throwaway devices isn’t an option, just act as white as you possibly can and just hope you get lucky and they ignore you.