I have a friend who refused to answer any questions at the border. They took him in for 6 hours of additional questioning, which he refused to answer. And they let him through. So they have no legal right to require you to answer any questions, but they have procedural authority to make your life difficult.
You're not obligated to unlock your phone, they're not obligated to let you cross the border. So you have a choice, turn around or unlock your phone.
If he was a US citizen he can’t be turned away at the border. Also still pretty sure a citizen has the right to refuse a search without a warrant.
I have a friend who refused to answer any questions at the border. They took him in for 6 hours of additional questioning, which he refused to answer. And they let him through. So they have no legal right to require you to answer any questions, but they have procedural authority to make your life difficult.
Right good point I didn't consider it might be someone from their own country