The Supreme Court said on Thursday that it would dismiss a case about emergency abortions in Idaho, temporarily clearing the way for women in the state to receive an abortion when their health is at risk.

The one-sentence, unsigned decision declared that the case had been “improvidently granted,” meaning a majority of the justices had changed their minds about the need to take up the case now. It reinstates a lower-court ruling that had halted Idaho’s near-total ban on abortion and permitted emergency abortions at hospitals if needed to protect the health of the mother while the case makes its way through the courts.

The decision, which did not rule on the substance of the case, closely mirrored a version that appeared briefly on the court’s website a day earlier and was reported by Bloomberg. A court spokeswoman acknowledged on Wednesday that the publications unit had “inadvertently and briefly uploaded a document” and said a ruling in the case would appear in due time.

Chief Justice John G. Roberts Jr. announced the court’s decision from the bench, as is the custom for unsigned opinions.

Justice Ketanji Brown Jackson, who in part disagreed with the court’s decision and asserted that the justices should have addressed the case on its merits, read her dissent from the bench. Such a move is rare and signals profound disagreement.

The joined cases, Moyle v. United States and Idaho v. United States, focus on whether a federal law aimed at ensuring emergency care for any patient supersedes Idaho’s abortion ban, one of the nation’s strictest. The state outlaws the procedure with few exceptions unless a woman’s life is in danger.

The decision was essentially 6 to 3, with three conservative justices siding with the liberal wing, albeit with separate writings and reasoning, in saying they would drop the case.

The dispute was the first time the court grappled with the question of statewide restrictions on abortion, many of which swiftly took effect after the court eliminated a constitutional right to the procedure two years ago.

The ruling handed a temporary victory to the Biden administration, which had turned to the federal law as one of the few, if narrow, ways to challenge state abortion bans and preserve access after the court overturned Roe v. Wade.

It also amounted to a second win, however muted, for abortion rights in recent weeks. This month, the court rejected a challenge to the longstanding approval of a commonly used abortion pill, saying that an umbrella group of anti-abortion medical organizations and doctors bringing the case lacked standing to sue. Even as the decision preserved availability of the pill, the court did not rule on the merits of the case.

Still, just as with the abortion pill, the case involving emergency abortions — and the underlying question of the state versus federal law — will continue in the lower courts.

Advocates for abortion rights pointed to that possibility even as they welcomed the outcome.

“We are relieved for the moment, but hardly celebrating,” said Nancy Northup, the president and chief executive of the Center for Reproductive Rights, adding, “Women with dire pregnancy complications and the hospital staff who care for them need clarity right now.”

The attorney general of Idaho, Raúl Labrador, said during a news conference that he remained undeterred. “We feel pretty strongly that we’re going to win this case in the end,” he said, adding that he expected the lawsuit or a parallel case in Texas could reach the justices again.

The decision, arriving hours before the first presidential debate, underlined the stakes for the coming election, where abortion remains a priority for both campaigns. Access to abortion is broadly popular, and the issue has galvanized voters eager to overturn antiabortion referendums at the polls.

In a statement, President Biden celebrated the court’s decision.

“Today’s Supreme Court order ensures that women in Idaho can access the emergency medical care they need while this case returns to the lower courts,” Mr. Biden said. “No woman should be denied care, made to wait until she’s near death or forced to flee her home state just to receive the health care she needs.”

Idaho had asked the justices to intervene after an 11-member panel of the U.S. Court of Appeals for the Ninth Circuit temporarily blocked the law. In agreeing to hear the case, the justices had temporarily reinstated the ban.

Under Idaho law, abortion is illegal except in cases of incest, rape, some instances of nonviable pregnancies or when it is “necessary to prevent the death of the pregnant woman.” Doctors who perform abortions could face criminal penalties, prison time and loss of their licenses to practice medicine.

The Biden administration had asserted that the ban conflicted with federal law and that the federal law should override it. Idaho contended that the Biden administration had improperly interpreted the federal law in an effort to bypass state bans, effectively turning hospitals into legal abortion sites.

The liberal justices, along with Justices Amy Coney Barrett and Brett M. Kavanaugh and Chief Justice John G. Roberts Jr., all wrote or joined in concurring opinions. The court’s remaining conservatives, Justices Samuel A. Alito Jr., Clarence Thomas and Neil M. Gorsuch, dissented.

In her partial agreement and partial dissent, Justice Jackson wrote that she would have decided on the substance of the case and that the federal law at issue, known as the Emergency Medical Treatment and Labor Act, overrides Idaho’s strict ban.

Justice Elena Kagan, in a concurring opinion, said the practical outcome of the court’s decision would forestall harrowing consequences.

The federal law, she wrote, “unambiguously requires” that hospitals receiving Medicare funding provide whatever treatment is necessary to stabilize a patient, including pregnant women.

Justice Jackson agreed. When the court allowed Idaho’s abortion ban to temporarily go into effect, a “monthslong catastrophe” ensued that could have been averted, she wrote. Instead, she noted, “Idaho physicians were forced to step back and watch as their patients suffered, or arrange for their patients to be airlifted out.”

Dismissing the case, she warned, was cause for concern, a path that simply allowed the court “to avoid issues that it does not wish to decide.”

“There is simply no good reason not to resolve this conflict now,” she wrote.

Even as Justice Alito sided with Justice Jackson in saying that the court should have heard the case on its merits, he came to the opposite conclusion as her. The Idaho abortion ban applied to emergency room care, he wrote.

To the contrary, he added, the federal law requires hospitals receiving Medicare funding “to treat, not abort, an ‘unborn child.’”

He expressed regret that the court lacked the desire to wrestle with a polarizing issue.

“That question is as ripe for decision as it ever will be,” Justice Alito wrote. “Apparently, the court has simply lost the will to decide the easy but emotional and highly politicized question that the case presents.”

Justice Barrett, joined by Chief Justice Roberts and Justice Kavanaugh, appeared to chart something of a middle ground.

The case should play out, for now, in the lower courts, she wrote, where a more complete picture of the facts could emerge.

The parameters of the Idaho law had “significantly changed — twice” since the lawsuit began, she added, and the parties’ positions had “rendered the scope of the dispute unclear, at best.”

Eileen Sullivan contributed reporting.