Can law enforcement obtain a BC with a search warrant?
I would think so, since a search warrant is a form of Court Order. If the SW specifically called for the BC to be seized, or a certified copy of it to be made and then siezed, that would be an order from a court of competant jurisdiction, which is one of the allowed exemptions to only the principal being able to obtain the BC.
But just having a court order served on the Registrar of the State of Hawaii would be simplier.