THE US SUPREME Court struck down a Louisiana law regulating abortion clinics, reasserting a commitment to abortion rights over fierce opposition from dissenting conservative justices in the first big abortion case of Donald Trump’s presidency.

Chief Justice John Roberts joined with his four more liberal colleagues in ruling that the law requiring doctors who perform abortions have admitting privileges at nearby hospitals violates the abortion right the court first announced in the landmark Roe vs Wade decision in 1973.

In two previous abortion cases, Mr Roberts had favoured restrictions.

The Louisiana law is virtually identical to one in Texas that the court struck down in 2016.

“The result in this case is controlled by our decision four years ago invalidating a nearly identical Texas law,” Mr Roberts wrote, although he did not join the opinion written by Justice Stephen Breyer for the other liberals.

In dissent, Justice Clarence Thomas wrote: “Today a majority of the Court perpetuates its ill-founded abortion jurisprudence by enjoining a perfectly legitimate state law and doing so without jurisdiction.”

President Donald Trump’s two appointees, Justices Neil Gorsuch and Brett Kavanaugh, were in dissent, along with Justice Samuel Alito.

The presence of the new justices is what fuelled hopes among abortion opponents, and fears on the other side, that the Supreme Court would be more likely to uphold restrictions.

Nancy Northup, president and chief executive of the Centre for Reproductive Rights, said today’s decision by no means ends the struggle over abortion rights in legislatures and the courts.

“We’re relieved that the Louisiana law has been blocked today but we’re concerned about tomorrow.

“With this win, the clinics in Louisiana can stay open to serve the one million women of reproductive age in the state.

“But the Court’s decision could embolden states to pass even more restrictive laws when clarity is needed if abortion rights are to be protected,” Northup said.

Early last year, Mr Roberts joined with the four liberal members of the court to grant that request and keep the law on hold.

Mr Roberts’ vote was a bit of a surprise because he voted in the Texas case to uphold the clinic restrictions.

It may have reflected his new role since Justice Anthony Kennedy’s retirement as the court’s swing justice, his concern about the court being perceived as a partisan institution and respect for a prior decision of the court, even one he disagreed with.

Mr Roberts did not write anything explaining his position at the time, but he had never before cast a vote on the side of abortion rights.

The regulations at issue in Louisiana are distinct from other state laws making their way through court challenges that would ban abortions early in a pregnancy.

Those include bans on abortion once a foetal heartbeat is detected, as early as six weeks, and the almost total ban passed in Alabama.