This is confusing; what happens to you if you refuse a warantless search of your property?
I'm a US citizen returning home. Do they just... send me back out of the country? :) I don't suppose they'd have the grounds to arrest me since there is no law that I can see being broken. I suppose they could keep the device until such time that a warrant could be obtained to digitally search / break into the device (but that requires some reasonable suspicion - simply refusing a warantless search isn't it).
As a citizen they cannot block you from returning to the country. What they can do however is seize your devices (and briefly your person) and other property.
Not for this they can't. They can seize your belongings but they can't detain you for something that isn't a crime and they cannot prevent you from entering the country if you're a citizen. You have an absolute right per Supreme Court rulings to enter the country unconditionally as a citizen
I'm a US citizen returning home. Do they just... send me back out of the country? :) I don't suppose they'd have the grounds to arrest me since there is no law that I can see being broken. I suppose they could keep the device until such time that a warrant could be obtained to digitally search / break into the device (but that requires some reasonable suspicion - simply refusing a warantless search isn't it).