If you're a US citizen, I believe they can seize your device indefinitely, and detain you for up to two days. They are required to let you eventually back into the country though.

(If you're not a citizen, all bets are off)

You dont have protectiond of US law on the border, inside the border and barely if you are a citizen far away from border. Realistically.

And also actually per law. And yes, being forced to give out passwords and make profiles public as a rputine thing is much worst then being forced to give out password when there is actual warrant.

CBP has absolutely put me in jail (not prison) for refusing to answer questions (including the strip search and being put in chains and handcuffs). As well as threatening to revoke my passport (though they could not). On another occasion they threatened to deport me even though I'm a US citizen. On yet another, they faked a drug dog hit then dragged me to multiple hospitals, racking up bills in my name while claiming I was packing drugs up my ass. I am still being chased by debt collectors for the last one.

I've contacted multiple lawyers and the answer got was they've tried cases like these before and they always lose so they don't take them anymore. Though this was pre-Trump, now it's suddenly in vogue to take up longshot border or immigration cases.