New York Times

WASHINGTON — The Supreme Court on Monday let stand a decision temporarily blocking an Arizona law that limits the availability of medicinal, nonsurgical abortions. As is its custom when it denies review, the court gave no reasons for its action.

The law, enacted in 2012, requires abortion providers to comply with a 2000 protocol from the Food and Drug Administration for mifepristone, an abortion-inducing drug that is sometimes called RU-486. The Legislature said the law was meant to “protect women from the dangerous and potentially deadly off-label use of abortion-inducing drugs.”

The 2000 protocol calls for the drug to be given in higher doses than is customary today, and only in the first seven weeks of pregnancy.

In the years since the protocol was issued, doctors have found that a lower dose of the drug is effective and that it can be taken safely through the ninth week of pregnancy.

Under the protocol required by the Arizona law, many women would be forced to have unnecessary surgical abortions, according to Planned Parenthood, which sued to block enforcement of the law. The group added that the law would make it hard for women in Northern Arizona, where only medicinal abortions are offered by the sole clinic there, to obtain abortions at all.

In June, a unanimous three-judge panel of the United States Court of Appeals for the Ninth Circuit, in San Francisco, blocked the law, saying it had imposed an “undue burden” on the right to abortion. The meaning and proper application of the undue-burden standard, announced by the Supreme Court in Planned Parenthood v. Casey in 1992, have divided the lower courts.

Two federal appeals courts have upheld laws restricting medicinal abortions in Texas and Ohio using a relaxed understanding of the scrutiny required by the standard. They ruled that it was enough to find that the laws were rationally related to the goal of protecting women’s health.

The Ninth Circuit, by contrast, said the undue-burden standard required it “to weigh the extent of the burden against the strength of the state’s justification.”

Judge William A. Fletcher, writing for the court, said that such weighing of the competing interests warranted blocking the Arizona law from going into effect. “Arizona has presented no evidence whatsoever that the law furthers any interest in women’s health,” he wrote. On the other side of the balance, he said, the law delayed and deterred abortions by making them more costly, cumbersome and dangerous.

“For a significant number of women, the law will ban medication abortions outright,” Judge Fletcher wrote, “because many women do not discover they are pregnant” in the seven-week period allowed under the F.D.A. protocol.

Thomas C. Horne, Arizona’s attorney general, urged the Supreme Court to hear the state’s appeal in order to give lower courts guidance on how to apply the undue-burden standard. He said the continued availability of surgical abortions in Arizona was enough to satisfy the standard.

In response, Planned Parenthood told the justices that they should not hear the case, Humble v. Planned Parenthood Arizona, No. 14-284, for three reasons: It was still at an early stage, a related state challenge was pending, and the precise meaning of the Arizona law remained unresolved.

Under one reading of the law, it banned all medicinal abortions by requiring adherence to F.D.A. protocols. That is because the F.D.A. has never approved the second drug, misoprostol, for use in abortions.

In 2013, the Supreme Court dismissed a case concerning a similar Oklahoma law that it had agreed to hear after the Oklahoma Supreme Court interpreted the law to ban all medicinal abortions.

Mr. Horne said the correct reading of the Arizona law allowed a role for the second drug.

The Supreme Court has not decided a major abortion case since 2007, when it upheld the federal Partial-Birth Abortion Ban Act.