By Lawrence Hurley and Andrew Chung
WASHINGTON (Reuters) - The U.S. Supreme Court on Wednesday heard arguments in a case that could upend the landmark 1973 Roe v. Wade ruling legalizing procedure nationwide, with liberal justices warning against ditching important legal precedents while some conservatives signaled support for the restrictive Mississippi law at issue.
The court, which has a 6-3 conservative majority, is hearing at least 70 minutes of oral arguments in the southern state's appeal to revive its ban on abortion starting at 15 weeks of pregnancy. Lower courts blocked the Republican-backed law.
Jackson Women's Health Organization, the only abortion clinic in Mississippi, challenged the law and has the support of Democratic President Joe Biden's administration. A ruling is expected by the end of next June.
Roe v. Wade recognized that the right to personal privacy under the U.S. Constitution protects a woman's ability to terminate her pregnancy. The Supreme Court in a 1992 ruling called Planned Parenthood of Southeastern Pennsylvania v. Casey reaffirmed abortion rights and prohibited laws imposing an "undue burden" on abortion access.
Conservative Justice Brett Kavanaugh noted that if Mississippi wins the case, such a ruling would not prohibit abortion nationwide but would let states regulate it as they see fit.
"You are not arguing somehow that the court somehow has the authority to prohibit abortion," Kavanaugh told Mississippi's lawyer, Scott Stewart. "You are arguing the constitution is silent and therefore neutral."
"Why is 15 weeks not enough time" for a woman to decide to have an abortion, Conservative Chief Justice John Roberts asked.
Liberal Justice Stephen Breyer quoted from the Supreme Court's Casey ruling, which stated that the court should not bow to political pressure in overturning Roe and that such a ruling would "subvert the court's legitimacy."
Liberal Justice Sonia Sotomayor questioned Stewart on whether if Roe were overturned then other major precedents including those on gay rights might also be threatened.
"The issue of when life begins has been hotly debated by philosophers since the beginning of time," Sotomayor said. "It's still debated in religions. So when you say this is the only right that takes away from the state the ability to protect a life, that's a religious view, isn't it, because it assumes that a fetus is life?"
Anti-abortion advocates believe they are closer than ever to overturning Roe, a longstanding goal for Christian conservatives.
Sotomayor said Mississippi brought its new challenge purely because of changes on the Supreme Court, which has become more conservative.
"Will this institution survive the stench this creates?" Sotomayor asked, saying that it would give the impression that the Constitution and its interpretation is based purely on politics. "If people think it is all political ... how will the court survive?"
Roberts expressed some skepticism about overturning court precedents, noting that "it's going to be a long list" of past rulings that the justices currently might think were incorrectly decided.
Mississippi's is one of a series of restrictive abortion laws passed in Republican-governed states in recent years. The Supreme Court on Nov. 1 heard arguments over a Texas law banning abortion at around six weeks of pregnancy but has not yet issued a ruling.
Liberal Justice Elena Kagan cited the importance of the court adhering to precedent "to prevent people from thinking this court is a political institution that will go back and forth depending on what part of the public yells the loudest and preventing the people from thinking the court will go back and forth based on the court's membership."
The Roe and Casey decisions determined that states cannot ban abortion before a fetus is viable outside the womb, generally viewed by doctors as between 24 and 28 weeks.
A 15-week ban is not a "dramatic departure from viability," Roberts said.
Roberts questioned whether viability was a central issue in the Roe or Casey rulings. The chief justice's question indicated he might be willing to uphold the Mississippi law by saying that viability was not central to earlier abortion decisions, a position abortion rights advocates hotly contest.
Mississippi's 15-week ban directly challenged the viability finding. Even if the court does not explicitly overturn Roe, any ruling letting states ban abortion before fetal viability outside the womb would raise questions about how early states could prohibit the procedure. In the 1992 Casey ruling, the court said Roe's "central holding" was that viability was the earliest point at which states could ban abortion.
"The right of a woman to choose, the right to control her own body, has been clearly set since Casey and never challenged. You want us to reject that line of viability and adopt something different," Sotomayor told Stewart.
Mississippi is among 12 states with so-called trigger laws designed to ban abortion if Roe v. Wade is overturned. Additional states also likely would move quickly to curtail abortion access.
Hundreds of protesters from both sides of the abortion debate rallied outside the white marble neoclassical courthouse ahead of the arguments. Anti-abortion protesters held huge signs reading "abortion is murder," some carrying Christian crosses. Abortion rights activists chanted "what do we want? Abortion access. When do we want it? Now."
If Roe were overturned or limited, large swathes of America could return to an era in which women who want to end a pregnancy face the choice of undergoing a potentially dangerous illegal abortion, traveling long distances to a state where the procedure remains legal and available or buying abortion pills online. The procedure would remain legal in liberal-leaning states, 15 of which have laws protecting abortion rights.
(Reporting by Lawrence Hurley and Andrew Chung; Additional reporting by Gabriella Borter, Jan Wolfe and Julia Harte; Editing by Will Dunham)