I had long wondered about the legality of extendable batons, such as ASP, here in Hawaii. It seems no two gun stores would ever give me the same response as to whether it was legal to carry. I finally emailed HPD directly and this was the response I got.
Hope you’re having a good morning. The Hawaii Revised Statute or City and County Revised Ordinance had no law stating the public are not allowed to carry a collapsible baton. Collapsible baton is used in a commission of a crime than the person shall be arrested for the offense.
I saved the email just in case for whatever reason I needed some sort of documentation of it.
I later inquired to an officer in person of his veiwings to the legality. He informed me that carrying it, and using it for self defense was perfectly legal. But if at any point you are "playing around" with it, or for whatever reason have it extended in a non emergency circumstance, then you would be brandishiing a dangerous weapon and could be arrested. As for wearing it out an open on the belt, he said that it is in the same vein as wearing a fixed blade knife, where while there may be no specific law against it, it may be up to the officers discrection to ask you to remove it as it is causing a "public disturbance". And that not all officers may be 100% keen on the specifics of the law, and will er on the side of caution.
For the record, while I do once in awhile still carry the baton on me here and there, I find it too heavy and too much a burdon on normal day to day functions. But I did in the past carry it when I felt the need for an added deterrent or layer of defense that pepper spray didn't always provide. Like when I used to deliver pizzas in Wahiawa (always with my managers approval).