MANY SUPREME COURT cases are complicated. Dobbs v. Jackson Women’s Health Organization, which concerns Mississippi’s severe 2018 abortion law, is not one of them. The court’s conservative majority, which chose to take the case this week, must choose: Will the justices unravel decades of precedent to achieve an ideological victory on the most hot-button of issues, or will they preserve the credibility of their institution? Mississippi flagrantly transgressed the court’s settled abortion jurisprudence in a scheme designed to produce precisely this Supreme Court showdown. In an instant, the court would burn a precious store of legitimacy if it upheld Mississippi’s brazen breach of long-settled precedent.

Taking the case, the court announced Monday that it would consider “whether all pre-viability prohibitions on elective abortions are unconstitutional.” Until this point, the answer has been obvious: Yes, explicitly and definitively. “In an unbroken line of decisions over the last fifty years, this Court has held that the Constitution guarantees each person the right to decide whether to continue a pre-viability pregnancy,” lawyers for the Jackson Women’s Health Organization, the only abortion clinic in Mississippi, wrote. “Yet Mississippi passed a law banning abortion after 15 weeks of pregnancy — months prior to viability.”

Following Roe v. Wade, the 1992 Planned Parenthood v. Casey ruling declared the states may not place “undue burdens” on women seeking abortions before their fetuses are viable. Banning abortion at 15 weeks, when viability comes at 23 or 24 weeks, is a bald-faced violation of this principle. Mississippi officials argue that fetus viability is a poor standard on which to restrict what states may do, as the line could move around depending on medical technology. Yet court after court has applied it successfully, and there is no disagreement on the matter among the appeals courts. In this case, the right-leaning U.S. Court of Appeals for the Fifth Circuit had no trouble condemning the Mississippi law under the Supreme Court’s unambiguous guidance. Indeed, the biological viability line has not moved since Casey, offering the court little ground for revisiting the standard.

The only conceivable reason the justices have to reassess this settled law is that the court’s composition has changed since the last time it considered a major abortion case. At least four justices must vote to accept a case, meaning that the court’s decision to take on the Mississippi dispute likely indicates that there are at least four votes to upend the precedent, and that those justices who insisted on taking the case believe there may be more than that.

The justices may try to disguise their gutting of abortion rights as a revision to, rather than a repudiation of, Roe and Casey. But no one should mistake an affirmation of the Mississippi law for what it would be: rank opportunism disguised as principle, delivering a desired policy outcome at the expense of the law’s stability, the basic principles of judging and the court’s moral authority.

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