of course, the big question is, how would they know?
im just curious, because my father has an unregistered rifle he got in the 70's.
§134-3 Registration, Mandatory, Exceptions. (a) Every person arriving in the State who brings or by any other manner causes to be brought into the State a firearm of any description, whether usable or unusable, serviceable or unserviceable, modern or antique, shall register the firearm within three days after arrival of the person or of the firearm, whichever arrives later.
§134-3 ( d) Registration shall not be required for:
(1) Any device that is designed to fire loose black powder or that is a firearm manufactured before 1899;
(2) Any device not designed to fire or made incapable of being readily restored to a firing condition; or
(3) All unserviceable firearms and destructive devices registered with the Bureau of Alcohol, Tobacco, and Firearms of the United States Department of Justice pursuant to Title 27, Code of Federal Regulations.
Registration is not mandatory for rifles and shotguns acquired in the state of Hawaiʻi prior to July, 1994. However, one permit per rifle or shotgun was required for acquisitions between 1981 and July, 1994.
So if your father has it already in Hawaii (local resident), it should be good, but if he lives in another state and wants to bring it to Hawaii, he would need to register it.