I believe there was a defcon talk about this but for the life of me I can't find it. My advice is to epoxy your lightning port closed (or snip the data connection inside the phone) and use wireless charging exclusively.

edit: It was the Signal founder. https://appleinsider.com/articles/21/04/21/signal-hacks-cell...

what if its a laptop now?

Buy a laptop that has a charging port. Then same advice applies.

But I would just format it.

My guess is it would be like setting up a trap gun and putting a sign on the door warning about it. Still illegal. But I'm a rando on the Internet and a loooooong ways from being any kind of lawyer, and I didn't stay in a Holiday Inn Express last night, either.

What do you think would happen to a regular person performing such an act? Would it be like Texas Chainsaw Massacre or a James Bond movie?

Huh? I'm asking about the realistic outcome, whether that be denial of border crossing, criminal charges, or they choose to not examine the device and let you through.

now what if you bought the phone off craigslist?

That's likely not relevant since during a border crossing your identity has already been verified.

"how was i supposed to know the phone i bought on craigslist had a payload?"

plausible deniability.

edit: please dont actually do this.

What if you planted a bomb in a package on your doorstep with instructions on it telling people not to open it? What if the package thief stealing your package opens it and causes an explosion injuring themselves and maybe others?

You're describing a (digital) booby trap. Since you're knowingly targeting law enforcement officers, I'm not sure legal theory factors into whether you could get away with it in practice but even theoretically the answer is probably no, that's a computer crime.