The decision overrides two lower federal courts that had upheld an injunction.
The Supreme Court on Monday allowed Idaho to proceed with enforcement of a new law aimed at prohibiting gender-affirming care for minors.
The decision overrides two lower federal courts that had upheld an injunction against the law as litigation over the merits continues.
The decision was backed by all six of the high court's conservative members. The three liberal justices -- Sonia Sotomayor, Elena Kagan and Ketanji Brown Jackson -- indicated they would have kept the law on hold.
"Ordinarily, injunctions like these may go no further than necessary to provide interim relief to the parties," Justice Neil Gorsuch wrote in a statement concurring with the court's decision. "In this case, however, the district court went much further, prohibiting a state from enforcing any aspect of its duly enacted law against anyone."
The court did, however, allow the parents and two children who brought the case against the law to continue to obtain treatments during litigation. The children are said to be seeking puberty blockers and estrogen, which the families and their doctors say are critical for mental health.
In her dissent, Jackson argued the high court should have refrained from intervening in such a high-profile case at an early stage, disrupting what she described as the legal status quo.
"In my view, we should resist being conscripted into service when our involvement amounts to micromanaging the lower courts' exercise of their discretionary authority in the midst of active litigation," Jackson wrote.
In a joint statement, the American Civil Liberties Union and the ACLU of Idaho called the ruling an "awful result."
"While the court's ruling today importantly does not touch upon the constitutionality of this law, it is nonetheless an awful result for transgender youth and their families across the state," the joint statement read. "Today's ruling allows the state to shut down the care that thousands of families rely on while sowing further confusion and disruption. Nonetheless, today's result only leaves us all the more determined to defeat this law in the courts entirely, making Idaho a safer state to raise every family."