Washington (CNN) The Supreme Court Thursday blocked a Louisiana abortion access law from going into effect for now, dealing a victory to opponents of the law who argued it could decimate "safe and legal" abortions in the state.

The order was 5-4 with Chief Justice John Roberts joining the court's four liberals voting for the stay. New conservative Justice Brett Kavanaugh wrote a dissent.

Louisiana's Unsafe Abortion Protection Act has been blocked since its enactment in 2014, and like a similar Texas law the court previously struck down, requires a doctor to have admitting privileges at a hospital within 30 miles of the facility where the abortion is performed.

Louisiana argues that the law is necessary to provide a higher level of physician competence, but critics say there is no medical justification for the law and it amounts to a veiled attempt to unlawfully restrict abortion.

The Supreme Court said in 2016 that the restrictions in the Texas law constituted an undue burden on a woman's right to seek an abortion.

The Center for Reproductive Rights -- representing patients, clinics and doctors in the state -- had asked the justices to put the law on hold before it was slated to go into effect on Friday.

Thursday night's ruling would not prevent the court from eventually agreeing to take up the case and uphold the law in the future. Supporters of abortion rights fear that the court's conservative majority -- solidified by the addition of Donald Trump's nominees Neil Gorsuch and Kavanaugh -- will move to chip away at abortion rights if not eventually all but overturn the landmark Supreme Court opinions of Roe v. Wade and Planned Parenthood v. Casey.

Struck down, then reversed on appeal

In 2017, a district court judge struck down the Louisiana law in a 116-page opinion laced with references to the Supreme Court's decision in the Texas case , known as Whole Woman's Health. Judge John deGravelles, of the US District Court for the Middle District of Louisiana, an Obama appointee, said the Louisiana law would severely limit the number of providers available to perform abortions, result in the closure of clinics and "place added stress" on remaining facilities.

About 10,000 women a year seek abortions in the state and the challengers had shown that if the law were to go into effect, only one physician would be able to provide abortions in the state, he said.

"Even working an implausible seven-day week, it would be impossible for him to expand his practice to meet even half the state's need for abortion services," deGravelles wrote.

Louisiana appealed the case to the 5th US Circuit Court of Appeals, which had previously upheld the Texas law before the Supreme Court reversed it.

In a 2-1 ruling, a three-judge panel of the circuit court acknowledged in its opinion that it was beholden to the Supreme Court's opinion, but it distinguished the Louisiana law from the Texas law.

As a part of its reasoning, the majority rejected deGrevelles' finding that abortion providers in the state had made a "good faith" effort to get the necessary admitting privileges. Instead, they said that "the vast majority largely sat on their hands, assuming they would not qualify." The majority held that the law would not "impose a substantial burden on a large fraction of women" and that admitting privileges in Louisiana are easier to obtain because the state is less stringent in its requirements.

Kavanaugh dissents

While Kavanaugh cast his vote with the conservatives on the court, he wrote separately to explain his thinking.

Kavanaugh thought the majority's move to block the law was premature. He noted that Louisiana had already stated that if the justices had allowed the law to go into effect, the state would have commenced a 45-day "transition" period to review how it would impact the clinics.

No provider, the state promised, would be forced to immediately cease operations.

Kavanaugh said essentially that the 45-day period would allow parties to get a true sense of the impact of the law. If the challengers still thought the law imposed an undue burden they could bring their challenges at that time.

Louisiana currently has three clinics where four doctors perform abortions, and one doctor already has admitting privileges as required by the law and the question turns on whether the others would be able to obtain the privileges, he said.

"If they can, then the three clinics could continue providing abortions," Kavanaugh wrote. "And if so, then the new law would not impose an undue burden for purposes of" Supreme Court precedent, he wrote.

Notably, the other conservative justices, Samuel Alito, Clarence Thomas and Neil Gorsuch did not join Kavanaugh's dissent, suggesting they may not have agreed entirely with his reasoning.

Roberts again the swing vote

Thursday's action again demonstrates Roberts' role as the key vote on abortion in the Supreme Court, said CNN analyst and University of Texas law professor Steve Vladeck.

Justice Anthony Kennedy had cast the deciding vote to block the Texas access law, but was replaced by Kavanaugh last year. On Thursday, Roberts cast the vote to block the Louisiana law.

"Compared to the majority opinion Justice Kennedy joined three years ago striking down a deeply similar Texas law, the fact that Justice Kavanaugh dissented drives home that, on abortion cases, the chief justice is now the swing vote," Vladeck said.