Do I have to register my protection order in GU in order to get it enforced?
No. Guam state law gives full protection to an out-of-state protection order as long as you can show the officer a copy of the order and can truthfully tell the officer that you believe the order is still in effect. It does not have to be entered into the state or federal registry in order to be enforced by a Guam police officer, but the officer does need to believe that it is a valid (real) order.
If you do choose to register it with the court, it will be given "full faith and credit" by the courts of Guam and enforced as if it were issued on Guam.*
* 19 G.C.A § 14105(b)