Failing to understand who has legal authority over a child can lead to missed court deadlines, violated parenting orders, police involvement during exchanges, or loss of decision-making power over medical care, schooling, or travel. Child custody is the legal arrangement that assigns parental rights and responsibilities for a minor child. It usually has two parts: legal custody, which covers major decisions about the child's welfare, and physical custody, which covers where the child lives and how parenting time is shared. Custody may be sole or joint, and it can be ordered by agreement or by a court.

In practice, custody determines who can consent to treatment, enroll a child in school, authorize activities, or decide where the child will reside. That can matter immediately in emergencies, including transport to a trauma facility such as Tripler Army Medical Center after a serious crash or sudden weather-related incident. A parent without legal custody may have limited authority to make those decisions unless a court order says otherwise.

In Hawaii, courts decide custody based on the child's best interests under Hawaii Revised Statutes section 571-46. The court may consider each parent's relationship with the child, safety, stability, and any history of family violence. Hawaii also uses the Uniform Child-Custody Jurisdiction and Enforcement Act in HRS chapter 583A to decide which state has authority to issue or enforce a custody order. Custody rulings often affect visitation, child support, relocation, and protective orders.