Law enforcement hacking into your device is acceptable. Evidence on your device remains admissable with probable cause, a warrant or a judge who likes the police / dislikes you.

Some judges will hold you in contempt for failing unlock your own device. (fourteen years is the record on contempt jail terms). So YMMV once youre facing charges.

Theres also a forgone conclusion rule. If the prosecutors can show sufficient evidence to a crime exists on your device, you can be compelled to open it. I do not know how this proof happens.

Also some judges (including SCOTUS by a ruling) just dont care if the evidence of a crime was legally obtained, they let it be admissible because locking you away is more important than state actors following protocols that preserve civil rights. Id est, the whole of the fourth and fifth amendments to the Constitution of the United States are as slippery as Schrödinger's cat.