In joining with the liberal justices, perennial swing vote Justice Anthony Kennedy helped deliver a victory to abortion rights activists and signaled the court's majority in their favor could continue regardless of the presidential election and the filling of the empty seat on the bench left by the death of conservative Justice Antonin Scalia.
Justice Stephen Breyer wrote the majority opinion, which was joined in full by Kennedy. Breyer wrote that despite arguments that the restrictions were designed to protect women's health, the reality is that they merely amounted to burdening women who seek abortions.
"There was no significant health-related problem that the new law helped to cure," Breyer wrote. "We agree with the District Court that the surgical-center requirement, like the admitting-privileges requirement, provides few, if any, health benefits for women, poses a substantial obstacle to women seeking abortions, and constitutes an "undue burden" on their constitutional right to do so."
Justice Ruth Bader Ginsburg joined Breyer's opinion and wrote a brief concurring opinion, which focused on what she called women in "desperate circumstances."
"When a State severely limits access to safe and legal procedures, women in desperate circumstances may resort to unlicensed rogue practitioners, faute de mieux, at great risk to their health and safety," she wrote.
The ruling will have reverberations on the presidential election, where the fate of the Supreme Court has been front-and-center after the death of Scalia in February. Senate Republicans have refused to act on President Barack Obama's nomination of Judge Merrick Garland, leaving the court with eight justices.
But Monday's ruling signals that even if Republicans were to name that replacement, the court still has a five-justice majority that could rule against abortion restrictions. And if Hillary Clinton were to win, the majority could even grow.
Hillary Clinton immediately praised the ruling.
"SCOTUS's decision is a victory for women in Texas and across America. Safe abortion should be a right—not just on paper, but in reality. -H"
President Barack Obama said he is "pleased" by the ruling.
"We remain strongly committed to the protection of women's health, including protecting a woman's access to safe, affordable health care and her right to determine her own future, the President said.
The court's decision has major implications for the future political battles over abortion beyond Texas.
Anti-abortion activists since Roe v. Wade have worked to pass a slew of laws across the country restricting abortions or making them more difficult, like the law struck down in Texas.
But Monday's ruling strengthened the premise of the 1992 case Planned Parenthood v Casey, sending a message to states that might pass such laws and lower courts that would uphold them that they have a high hurdle to prove they're constitutional. The Casey ruling said that states could impose restrictions as long as they didn't impose an undue burden on the woman.
"By clarifying exactly what the 'undue burden' test requires, I suspect the majority was hoping to dissuade states like Oklahoma from continuing to pass laws that so directly challenge the central premise of Roe v. Wade -- that the Constitution protects a pregnant woman's right to an abortion in a meaningful percentage of cases," said Steve Vladeck, CNN contributor and professor of law at American University Washington College of Law.
"In the process, the Court today has called into question everything from categorical bans on abortions to so-called 'fetal heartbeat' restrictions, and perhaps plenty of other laws in between," Vladeck added.
Already, both sides signaled they intend to keep fighting.
"Our fight is far from over," Clinton said in a statement. "In Texas and across the country, a woman's constitutional right to make her own health decisions is under attack. In the first three months of 2016, states introduced more than 400 measures restricting access to abortion."
Texas Gov. Greg Abbott decried the ruling. "The decision erodes States' lawmaking authority to safeguard the health and safety of women and subjects more innocent life to being lost," the Republican governor said in a statement. "Texas' goal is to protect innocent life, while ensuring the highest health and safety standards for women."
"I'm disappointed in the Court's decision. But our fight to protect women's health & promote life will not stop here," House Speaker Paul Ryan tweeted
Kennedy the swing vote
All eyes were on Kennedy entering oral arguments -- a position the 79-year-old justice has often found himself in on the abortion issue.
Kennedy was one of the authors of Casey, but then disappointed supporters of abortion rights when he upheld the federal partial birth abortion ban in 2007. All eyes were on him for this case to see if he would take the opportunity to clarify Casey. Instead, as the most senior justice in the majority it was his choice to allow Breyer to write.
"The fact that Justice Kennedy gave away this opinion assignment and didn't write separately is striking," said Vladeck. "Kennedy has not only been the swing vote on abortion issues since he joined the Court in 1988, but he has written an opinion in virtually every major abortion case during that time, including the majority opinion in the Court's controversial 2007 decision upholding the federal ban on so-called 'partial-birth' abortions.
"It's not stunning that he sided with the liberals in striking down the Texas law in this case, but it is stunning that he didn't feel the need to explain why," Vladeck added.
Strong dissents from Thomas, Alito
Justices Clarence Thomas and Samuel Alito wrote dissents.
Thomas wrote a bitter dissent for himself, accusing the court of eroding the Constitution.
"The Court has simultaneously transformed judicially created rights like the right to abortion into preferred constitutional rights, while disfavoring many of the rights actually enumerated in the Constitution," Thomas wrote. "But our Constitution renounces the notion that some constitutional rights are more equal than others. ... A law either infringes a constitutional right, or not; there is no room for the judiciary to invent tolerable degrees of encroachment. Unless the Court abides by one set of rules to adjudicate constitutional rights, it will continue reducing constitutional law to policy-driven value judgments until the last shreds of its legitimacy disappear."
While Thomas would have upheld the laws, in Alito's dissent, joined by Chief Justice John Roberts, the justices would have sent the laws back to the lower courts to be decided after more evidence was presented.
Alito accused the justices in the majority of fabricating claims for the attorneys in the case.
"Determined to strike down two provisions of a new Texas abortion statute in all of their applications, the Court simply disregards basic rules that apply in all other cases," Alito wrote. "The Court favors petitioners with a victory that they did not have the audacity to seek."
Alito thought the two provisions of the law should have been dealt with separately and he condemns the majority for failing to do that analysis.
"If some applications are unconstitutional, the severability clause plainly requires that those applications be severed and that the rest be left intact....How can the Court possibly escape this painfully obvious conclusion. Its main argument is that it need not honor the severability provision because doing so would be too burdensome."
Carrie Severino, chief counsel and policy director of the Judicial Crisis Network and former clerk to Thomas, said the ruling "made clear that some constitutional rights are more equal than others." In a statement, she added that "by throwing out the regular legal rules in order to carry water for the abortion industry, the Court has further threatened its own legitimacy. It's no wonder the Supreme Court is suffering record levels of disapproval with the American people."
Impact of the law
There were two provisions of the law at issue. The first said that doctors have to have local admitting privileges at nearby hospitals, the second says that the clinics have to upgrade their facilities to hospital-like standards.
Critics say if the 2013 law, known as H.B. 2, is allowed to go into effect it could shutter all but a handful of clinics in a state with 5.4 million women of reproductive age.
Texas countered that the law was passed in response to the Kermit Gosnell scandal. The Pennsylvania man was convicted in 2013 of first-degree murder for killing babies that were born alive in his clinic.
State Solicitor General Scott Keller argued in court papers that if the court were to uphold the law, an abortion clinic "will remain open in each area where one will close, meaning that over 90% of Texas women of reproductive age will live within 150 miles of an open abortion clinic."
A federal appeals court upheld the Texas law in 2015, and last spring a majority of the Supreme Court voted to stay that ruling pending appeal. The four conservative justices at the time: John Roberts, along with Thomas, Alito and the late Justice Antonin Scalia, publicly noted that they would have denied the stay.
Scene outside the court
Protesters gathered outside the court in the hot, humid weather said they were ready to continue the abortion battle at the ballot box in November.
Ilyse Hogue, president of NARAL Pro-Choice America, told CNN that the electoral fight would extend from the race for the White House, to the races in statehouses throughout the nation.
"I think it's a wake-up call to most Americans who value freedom, who value dignity that we need to get out and make our voices heard against a vocal minority, especially in November," Hogue said. "It's not just at the top of the ticket, but at the statehouse, too."
Teresa Stormes, 57, a CPA from Paragould, Arkansas, was visiting Washington with her children, Will Robbins, 18, and Ashley Robbins, 29. Even after a loss at the nation's highest court, people opposing abortion should turn to their local races and candidates, and their neighbors, she said.
"There's a lot of people on the planet and there's only a certain circle of people we can influence," Stormes said. "It's kind of like you have to go back to square one and be an example where you are and support life where you are."
Joe Aquilante, 42, a high school theology teacher from Philadelphia, said he had traveled down to Washington the previous weeks with other students and teachers from his school, expecting a ruling. When it was announced Monday, he said he had "mixed emotions."
"You know, I was saddened, but I'm emboldened as well because we've got to continue to fight," he said.
Fiorella Spalvieri, 53, a mental health administrator who was visiting Washington and walked over to the protest in support of pro-abortion rights groups, took a sober view of the ruling Monday: "I'm not sure the debate will ever be over."