WASHINGTON, Sept 13 (Reuters) - Abortion rights advocates on Monday urged the U.S. Supreme Court not to overturn the Roe v. Wade ruling that legalized abortion nationwide - a 1973 landmark imperiled in the legal fight over Mississippi's attempt to ban the procedure after 15 weeks of pregnancy.
"The fallout would be swift and certain. As abortion bans are enforced - or the threat of enforcement looms - large swaths of the South and Midwest would likely be without access to legal abortion," said lawyers for Jackson Women's Health Organization, the only abortion clinic in Mississippi.
"People would be harmed, and chaos would ensue, even in states that claim not to be prohibiting abortion directly," the lawyers added.
The court filing came in response to Mississippi Attorney General Lynn Fitch, a Republican, who said in papers filed with the court in July that the Roe v. Wade ruling and a subsequent 1992 decision that affirmed it were both "egregiously wrong."
The court has a 6-3 conservative majority.
Mississippi's July court filing marked the first time that the Republican-governed state, in seeking to revive a law blocked by lower courts, made overturning Roe v. Wade a central part of its argument. The 1973 ruling ended an era in which some states had banned abortion.
"Unless the court is to be perceived as representing nothing more than the preferences of its current membership, it is critical that judicial protection hold firm absent the most dramatic and unexpected changes in law or fact," lawyers for the Mississippi clinic said.
The Supreme Court's central role in the fight over abortion rights was highlighted on Sept. 1. In a late-night decision, the court allowed a Texas law that bans abortions after six weeks of pregnancy to stay in effect, setting off a firestorm of criticism from abortion rights advocates.
The court in May agreed to take up the Mississippi case and will hear it in its term that begins in October. Oral arguments have not yet been scheduled, with a ruling due by the end of June 2022.
It has been a longstanding aim of religious conservatives to overturn Roe v. Wade, which recognized that a constitutional right to personal privacy protects a woman's ability to terminate a pregnancy. The court in its 1992 decision, Planned Parenthood of Southeastern Pennsylvania v. Casey, reaffirmed the ruling and prohibited laws that place an "undue burden" on a woman's ability to obtain an abortion.
Roe v. Wade said that states could not ban abortion before the viability of the fetus outside the womb, which is generally viewed by doctors as between 24 and 28 weeks. The Mississippi law, enacted in 2018, would ban abortion much earlier than that. Other states like Texas have backed laws that would ban it even earlier.
After Jackson Women's Health Organization sued to block the 15-week ban, a federal judge in 2018 ruled against Mississippi. The New Orleans-based 5th U.S. Circuit Court of Appeals in 2019 reached the same conclusion.
The Supreme Court in 2016 and 2020 struck down restrictive abortion laws in Texas and Louisiana, but new justices appointed by Republican former President Donald Trump have moved the court further rightward.
The court's conservative majority includes the addition last year of Trump's third appointee, Justice Amy Coney Barrett, who during her Senate confirmation hearings declined to call Roe v. Wade a "super-precedent" invulnerable to being overturned. Barrett replaced liberal Justice Ruth Bader Ginsburg, an abortion rights champion who died last year.
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