A federal appeals court declared Friday that Mississippi’s ban on abortion at 15 weeks is unconstitutional, dealing a blow to those seeking to overturn the landmark Supreme Courtruling that legalized abortion nationwide.

The 5th U.S. Circuit Court of Appeals said U.S. District Judge Carlton Reeves ruled correctly when he blocked the Mississippi law from taking effect in 2018.

With the addition of conservative justices to the U.S. Supreme Court in recent years, several states have been enacting laws aimed at spurring court challenges that could eventually seek to overturn the court’s 1973 abortion rights ruling in Roe v. Wade.

“In an unbroken line dating to Roe v. Wade, the Supreme Court’s abortion cases have established (and affirmed, and re-affirmed) a woman’s right to choose an abortion before viability,” the appeals court judges wrote. “States may regulate abortion procedures prior to viability so long as they do not impose an undue burden on the woman’s right but they may not ban abortions.”

The only abortion clinic in Mississippi sued the state after Republican Gov. Phil Bryant signed the law. The clinic said it provides abortions until 16 weeks.

Mississippi legislators came back in 2019 and passed a more restrictive law to ban most abortions at about six weeks. The same federal district judge blocked that, too, and a legal fight over it continues.

The 5th Circuit based in New Orleans handles cases from Mississippi, Louisiana and Texas. It is generally considered one of the most conservative federal appellate courts.