What to do if border police ask to search your phone

Another consideration is what happens on the other side of the journey. Canada, Britain, Australia, and New Zealand, which all share intelligence with the U.S. government under the Five Eyes program, have different border privacy policies. Under Australian law, travelers do not have to unlock their phones. Canadian authorities, like U.S. authorities, say they will seize a phone if a traveler refuses to unlock it. New Zealand imposes a $5,000 fine for failing to unlock a phone, and Britain considers refusing to unlock a phone for police to be a counterterrorism offense.

Quite insane. Seems like the only real answer is a burner phone.

Make sure you've got a lock screen not based on biometrics and hand them your phone. They can't compel you to open it.