Courts in Arizona cannot interfere with decisions made by a parent who has sole legal custody of a child unless the decision is harmful to the child, the Arizona Supreme Court ruled.

The Supreme Court made its ruling after considering evidence in a case in which divorced parents disagreed over how one parent treated the child’s gender identification.

“The court must be mindful not to unnecessarily intrude on the sole legal decision-maker’s unshared authority to make major decisions concerning the child’s upbringing, even if those decisions conflict with expert opinion or the court’s own views on child rearing,” a justice wrote in the decision, representing a unanimous court.

In this case, the child is biologically male. The parents divorced when the child was 3, and they were awarded equal parenting time. The father was granted the right to make decisions over the child’s education, as well as medical and dental care.

The parents became at odds when the father the learned the mother was attempting to have the child, then 5, identify as a female. She discussed sex-reassignment surgery and hormone therapy with the child.

The child had been diagnosed with gender dysphoria of childhood, which is a difference between biological gender and expressed gender.

The father, though not as comfortable with the situation, agreed to counseling and to allow the child greater identification as a girl while at the mother’s home, including wearing girls’ clothing. The mother, however, allowed the child to wear the clothing in public, too.

When the parents’ dispute over the issue got to family court, the judge appointed a specific therapist for the child and an expert for the court, which the Supreme Court ruled went over the line and cut into the father’s authority.

“(The law) authorized the family court to impose a specific limitation on the sole legal decision-maker’s authority only when the other parent demonstrates that absent that limitation, the child would be physically endangered or the child’s emotional development would be significantly impaired,” the justice said.

The court said that despite “the complexity of the child’s situation,” those elements were not present in this case.

“Fit parents, like Father, frequently guide their children through complex situations without court interference,” the justice wrote.

The ruling — that the courts can’t interfere with the decision-making of parents in most situations — is good guidance for attorneys working with parents going forward.