The US supreme court on Monday struck down one of the harshest abortion restrictions in the country and potentially paved the way to overturn dozens of measures in other states that curtail access, in what might be the most significant legal victory for reproductive rights advocates since the right to abortion was established in 1973.

The 5-3 ruling will immediately prevent Texas from enforcing a law that would have closed all but nine abortion clinics. But in a coup for abortion rights supporters, the court also in effect barred lawmakers from passing health measures backed by dubious medical evidence as a way of forcing large numbers of abortion clinics to close.

Justice Stephen Breyer wrote the opinion for the majority and was joined by justices Ruth Bader Ginsburg, Sonia Sotomayor, Elena Kagan, and Anthony Kennedy, whose support was key to determining if the liberal or conservative bloc of the court would prevail.

“We conclude that neither of these provisions offers medical benefits sufficient to justify the burdens upon access that each imposes,” Breyer’s opinion read. “Each places a substantial obstacle in the path of women seeking a previability abortion, each constitutes an undue burden on abortion access … and each violates the Federal Constitution.”

The opinion went on to note that attorneys for Texas failed to mount any evidence that the law had made abortion safer.

The case began in 2013, when Texas Republicans, on the heels of an 11-hour filibuster by state senator Wendy Davis, passed one of the most expansive abortion restrictions in the country. The bill, known as House Bill 2, requires abortion providers to have staff privileges at a hospital within 30 miles of the clinic and requires clinics to meet expensive, hospital-like building and equipment standards.

Lawmakers claimed these were critical safety measures. But abortion providers argued that HB 2 was a gambit designed to shut clinics down in large numbers. On the day the admitting privileges requirement took effect, in November 2013, the number of Texas abortion clinics plummeted from 41 to 22. Today, there are 18. Had the requirement for clinics to meet hospital-like rules gone into effect, another nine would have shut down.

In its opinion on Monday, the majority agreed that Texas had failed to demonstrate a medical justification for its restrictions.

“We have found nothing in Texas’ record evidence that shows that, compared to prior law … the new law advanced Texas’ legitimate interest in protecting women’s health,” the opinion read. “We add that, when directly asked at oral argument whether Texas knew of a single instance in which the new requirement would have helped even one woman obtain better treatment, Texas admitted that there was no evidence in the record of such a case.”

The same argument was echoed in a concurring opinion by Ginsburg. “It is beyond rational belief that HB 2 could genuinely protect the health of women,” she wrote.

Monday’s ruling could give abortion providers across the county ammunition to strike down similar restrictions in the lower courts. Admitting privileges requirements and hospital-like regulations threaten to shutter more than a dozen abortion clinics in Alabama, Arkansas, Louisiana, Mississippi, Oklahoma, Tennessee and Wisconsin.

But after Monday’s ruling, those laws will almost certainly be struck down in the lower courts. Many more restrictions that have been in effect for years may also be in the crosshairs now.

At the heart of this case was a two-decade old dispute over how strictly states can regulate abortion, so long as they claim to be doing so for health purposes. A 1992 supreme court decision, Planned Parenthood v Casey, gave states the right to restrict abortion to protect women’s health as long as it didn’t create an “undue burden” for women seeking abortion. “An undue burden exists,” that decision reads, “and therefore a provision of law is invalid, if its purpose or effect is to place substantial obstacles in the path of a woman seeking an abortion.”

But the court never fully clarified the meaning of “undue burden”. Texas abortion providers argued that a law is an undue burden if it is medically unnecessary. Attorneys for Texas argued that courts should defer to the legislature’s knowledge of what is medically unnecessary, and a law is only an undue burden if it significantly impacts abortion access.

On Monday, the majority ruled that courts should in fact scrutinize the medical evidence behind burdensome abortion restrictions.

The decision was greeted with cheers from throngs of young women and reproductive rights activists gathered on the steps of the supreme court.

“I am beyond elated,” said Amy Hagstrom Miller, who runs the group of abortion clinics, Whole Woman’s Health, that headed up the lawsuit to overturn Texas’s abortion law. “With this clinic shutdown law, politicians forced Texas women seeking abortion to go to clinics that are further away or in another state, take more days off of work, lose income, find childcare, and arrange and pay for transportation to travel hundreds of miles. Today’s decision marks a turnaround for Texas and for our country.”

The decision will have a particularly great impact on low-income Latinas, who were thought to have the most trouble overcoming barriers to abortion access under HB 2, said Jessica González-Rojas, director of the National Latina Institute for Reproductive Health. “These are people who are least able to drive hundreds of miles to an abortion clinic,” she said.

In 2014, US district judge Lee Yeakel sided with Whole Woman’s Health and ruled key parts of HB 2 unconstitutional. A three-judge panel from the fifth circuit court of appeals, the most conservative circuit in the US, overturned his decision in June 2015. The four liberal justices plus Justice Anthony Kennedy blocked that requirement until the court could resolve the case. The supreme court agreed to take up the case in November and heard oral arguments on 2 March 2016.

Abortion clinics and their allies have mounted significant evidence that HB 2’s restrictions were both medically unnecessary and “devastating” to abortion access, in Miller’s words.

Briefs to the court from leading medical groups, such as the American Medical Association, emphasized that hospital admitting privileges are generally reserved for doctors who treat patients in an inpatient setting. Because abortion is an outpatient procedure with a low complication rate – the risk of a serious complication is between 0.05% and 0.2% – abortion providers rarely meet a hospital’s particular requirements.

In March, researchers with the Texas Policy Evaluation Project at the University of Texas-Austin found that with parts of HB 2 in effect, the average number of miles that many women traveled to get an abortion nearly quadrupled.

If Whole Woman’s Health had lost and the law had gone into effect, abortion access would have been restricted entirely to the large metropolitan centers of Dallas, Fort Worth, Austin and San Antonio. There wouldn’t have been a single clinic for 500 miles between San Antonio and the border with New Mexico.

Chief Justice John Roberts, Justice Samuel Alito and Justice Clarence Thomas dissented from Breyer’s opinion, with Thomas indicating that he would have voted to uphold the entire law. Roberts and Alito would have remanded the case back down to the lower courts for additional findings. On Monday, Alito took the rare step of reading his dissent aloud from the bench. He accused the majority of being hasty to rule and bending procedural rules because the topic was abortion.

This case was one of the most highly anticipated of this supreme court term, with legal experts of all ideological stripes expecting the outcome to set a major precedent on abortion rights. The US solicitor general, Donald Verrilli, joined oral arguments on the side of the abortion clinics. The court had not considered such a monumental abortion rights case since Casey in 1992. In that case, the court affirmed the right to abortion but laid a blueprint for decades of restrictions on the procedure.

Following the death of Justice Anontin Scalia, who likely would have voted to uphold the law, many observers expected the court to deadlock in this case along ideological lines. For abortion providers, this was a kind of doomsday scenario: A split would have upheld the fifth circuit court of appeals decision of June 2015 and forced half of Texas clinics to close.

A split also would have sent strong signals that abortion providers would lose their ongoing case against an admitting privileges law in Louisiana, which is also in the fifth circuit with Texas. That law threatens to close two out of four Louisiana abortion clinics; the provider with admitting privileges at a third abortion clinic has said he would quit and leave the state with only one clinic.

Molly Redden
@mtredden