Haw. Rev. Stat. § 327G-1
The State finds that all competent persons have the fundamental right to control decisions relating to their own mental health care, including the decision to accept or refuse all types of mental health treatment. The rights of individuals shall be respected when they have lost the capacity to participate actively in decisions regarding themselves or their mental health care and treatment. The laws of the State of Hawaii shall recognize the right of persons eighteen years of age or older and emancipated minors to make a written advance mental health care directive expressing their preferences and instructions regarding mental health care and treatment, including the consent to, or refusal of, that care and treatment, and to designate an agent or alternate agents to make mental health care decisions on behalf of the individual, when that individual later loses the capacity to make those decisions due to a mental illness.
HRS § 327G-1