Haw. Rev. Stat. § 52D-5: Powers of chief of police outside own county.

The chief of police of each county and any duly authorized subordinates shall have and may exercise all powers, privileges, and authority necessary to enforce the laws of the State, in a county other than the county in and for which the chief has been appointed, if:

(1) The exercise of such power, privilege, and authority is required in the pursuit of any investigation commenced within the county in and for which the chief has been appointed; and

(2) The concurrence of the chief of police of the county in which the power, privilege, and authority sought to be exercised is obtained.