The Texas Supreme Court upheld a state law on Friday that bans gender-transition medical treatment for minors, overturning a lower-court ruling that had temporarily blocked the law and dealing a blow to parents of transgender children.

The court, whose nine elected members are all Republicans, voted 8 to 1 in favor of allowing the law, which passed last year, to remain in effect. It bars doctors from prescribing certain medications to minors, like hormones and puberty blockers, and forbids them from performing certain surgical procedures, like mastectomies, on minors.

Parents of transgender youths, along with gay and transgender advocacy groups, argued that the ban should be blocked because it violated the Texas Constitution, in part by preventing parents from making what they felt were the best medical decisions for their children.

The argument is a powerful one in Texas, where protecting parental rights from government intervention has been an important goal, particularly for conservatives. But the court found that the argument fell short.

“We have never held that a fit parent’s interest in caring for her child free from government interference, though weighty, triggers heightened scrutiny of every statute,” Justice Rebeca A. Huddle wrote in the court’s opinion.

She wrote that the Legislature had made “a permissible, rational policy choice to limit the types of available medical procedures for children, particularly in light of the relative nascency of both gender dysphoria and its various modes of treatment.”