Keliinui, no it is not Hawaii legal. Prohibited---Semi-automatic handguns which accept a detachable magazine and have two or more of the following features:●Magazine that attaches to the pistol outside of the pistol grip.●Threaded barrel capable of accepting a barrel extender,flash suppressor, forward handgrip, or silencer.●Barrel shroud.●Manufactured weight of 50oz or more (unloaded).●Centerfire pistol with an overall length of 12 inches or more.●Semi-automatic version of an automatic firearm

Due to the barrel being shorter the 16" this is classified as a pistol and has to many banned pistol features, it is not allowed in HI

Keliinui, unfortunately it is not due to prohibited items listed : Magazine that attaches to the pistol outside of the pistol grip. ●Threaded barrel capable of accepting a barrel extender,flash suppressor, forward hand grip, or silencer .●Barrel shroud. ●Manufactured weight of 50oz or more (unloaded). ●Centerfire pistol with an overall length of 12 inches or more. Details here : budsgunshop.com/feeds/state_reg/hawaii_restrictions.pdf