Here is the text of Hawaii laws concerning knives (updated4/23/2002). I see no mention of double-edged blades.
§134-51 Deadly weapons; prohibitions; penalty. (a) Any person, not authorized by law, who carries concealed upon the person's self or within any vehicle used or occupied by the person or who is found armed with any dirk, dagger, blackjack, slug shot, billy, metal knuckles, pistol, or other deadly or dangerous weapon shall be guilty of a misdemeanor and may be immediately arrested without warrant by any sheriff, police officer, or other officer or person. Any weapon, above enumerated, upon conviction of the one carrying or possessing it under this section, shall be summarily destroyed by the chief of police or sheriff. (b) Whoever knowingly possesses or intentionally uses or threatens to use a deadly or dangerous weapon while engaged in the commission of a crime shall be guilty of a class C felony. [L 1937, c 123, §1; RL 1945, §11114; RL 1955, §267-25; HRS §727-25; ren L 1972, c 9, pt of §1; am L 1977, c 191, §2; am L 1983, c 267, §1; gen ch 1985; am L 1989, c 211, §10; am L 1990, c 195, §3 and c 281, §11; am L 1992, c 87, §4; am L 1993, c 226, §1; am L 1999, c 285, §2]
§134-52 Switchblade knives; prohibitions; penalty. (a) Whoever knowingly manufactures, sells, transfers, possesses, or transports in the State any switchblade knife, being any knife having a blade which opens automatically (1) by hand pressure applied to a button or other device in the handle of the knife, or (2) by operation of inertia, gravity, or both, shall be guilty of a misdemeanor. (b) Whoever knowingly possesses or intentionally uses or threatens to use a switchblade knife while engaged in the commission of a crime shall be guilty of a class C felony. [L 1959, c 225, §1; Supp, §264-9; HRS §769-1; ren L 1972, c 9, pt of §1; am L 1990, c 195, §4]
[§134-53] Butterfly knives; prohibitions; penalty. (a) Whoever knowingly manufactures, sells, transfers, possesses, or transports in the State any butterfly knife, being a knife having a blade encased in a split handle that manually unfolds with hand or wrist action with the assistance of inertia, gravity or both, shall be guilty of a misdemeanor. (b) Whoever knowingly possesses or intentionally uses or threatens to use a butterfly knife while engaged in the commission of a crime shall be guilty of a class C felony. [L 1999, c 285, §1]
[§302A-1134.6] Zero tolerance policy. (a) Any child who possesses, sells, or uses a dangerous weapon or switchblade knife, while attending school or while attending department-supervised activities held on or off school property, may be excluded from attending school for up to ninety-two school days, as determined by the principal and approved by the superintendent or other individuals designated pursuant to rules adopted by the board... (f) For purposes of this section: (1) "Dangerous weapon" means a dirk, dagger, butterfly knife, blackjack, slug shot, billy, metal knuckles, or other instrument whose sole design and purpose is to inflict bodily injury or death; provided that firearms are excluded from this definition; (3) "Switchblade knife" is as defined in section 134-52.