Citizens may, indeed, not be barred from re-entering, but there's absolutely nothing, anywhere that says we can't be made to wait unconscionably long before entry, or that we can be allowed to re-enter without our devices.
That constitutes de facto detention and yes, there's absolutely something that governs it.
Unfortunately ICE/CBP has policies [1] in place to require the phone's password that they believe are legitimate per 8 USC § 1357(a) (3). It's likely that only a court ruling weighing the policy regarding this statute against the bill of rights would make them change.
