By the end of this academic year, Roe may be gone.

It is a privilege to find yourself in college when history strikes. College offers the leisure and resources to digest and discuss the significance of a great historical moment in ways that may bear fruit for life. You might have the privilege to do just that, thanks to a Supreme Court decision to be argued December 1 and decided by the summer.

In Dobbs v. Jackson Whole Women’s Health Organization, the Supreme Court will pass on the constitutionality of a Mississippi abortion law. The Court may very well use this case to overturn Roe v. Wade (1973) and Planned Parenthood v. Casey (1992), the decisions that established and then reaffirmed a constitutional right to elective abortions. This would make Dobbs the most important case in a half century and its resolution one of the most important events of this century.

Dobbs may overturn Roe for lack of alternatives, if nothing else. Everyone (rightly) assumes that Dobbs will find a way to uphold the Mississippi law, which bans abortions from 15 weeks with exceptions for medical emergencies and severe fetal abnormalities. But to do that, the Court would have to scrap Roe and Casey, because those cases forbid bans to begin before the child becomes viable (capable of surviving outside the womb), around 24 weeks. If the Court upholds a 15-week ban by scuttling those precedents, it will eliminate along with them the constitutional right to abortion unless it replaces their viability line with a new test for abortion laws. This new test would have to allow abortion bans to begin sometime after conception but before 15 weeks. And the trouble is that it is impossible to find a line between those points that would have any basis in legal sources—text, history, precedent, and the like.

The text of the Constitution is useless here because it never mentions abortion, much less defines the contours of a right to abort. Roe claimed to locate the right in the Due Process Clause of the 14th Amendment, ratified just after the Civil War, which simply prevents states from denying someone “life, liberty, or property, without due process of law”—i.e., without a fair trial and the like.

Historical practice also offers no support for a line between conception and 15 weeks of pregnancy. The only thing that happens between those points that has a remote connection to any historical legal rule is “quickening”—when the mother first feels the fetus move. At common law—the law built up over time by the courts of England, and inherited by our colonies and states—quickening was the point after which abortions could be criminalized. Roe inferred from this that before quickening, there was a common law right to obtain an abortion. Not so.

From the Medieval roots of the common law until the 1970s, no legal text or authority had ever asserted such a right, and Roe’s reading of one was later debunked. The truth is that while criminal penalties began only with quickening, the common law subjected even pre-quickening abortions to a number of legal burdens that prove it was never considered a right. For example, contracts to perform abortions were deemed void on the ground that they were contracts to engage in something contrary to law or policy. Houses for performing abortions were subject to be closed, with legal penalties for anyone resuming their use. Most strikingly, even pre-quickening abortion functioned as a kind of felony when it came to felony murder—a legal doctrine allowing you to be convicted of murder if you accidentally caused someone’s death while performing another unlawful act. Because early abortion was considered unlawful (even though not criminal), even the most innocent accidental cause of the mother’s death—or of the child’s, if it was born alive, however briefly—would lead to a murder conviction for the abortionist. That wouldn’t have been so if abortion were considered a right.

If not text or history, what about precedent?  Is there any basis in the Court’s previous cases for drawing a line between conception and 15 weeks, to mark the period of pregnancy in which states may ban abortions?  No. Again, the Court’s precedents uniformly reject abortion bans until 24 weeks of pregnancy. The only precedent that rests anything on any point between 0 and 15 weeks is Roe, which created a set of rules relying on trimesters. The first trimester ends at 12 weeks, which is indeed between 0 and 15. But Roe said only that 12 weeks was when states could begin regulating the abortion procedure, and only for the purpose of protecting the mother’s safety. It explicitly rejected the notion that at 12 weeks states could begin imposing abortion bans for the sake of protecting the child’s life.

Might the Court simply make up a new line, based on whatever point in the unborn child’s early development seems morally significant?  But which line?  Between conception and 15 weeks, the most intuitively striking change is the emergence of the child’s heartbeat. But that occurs around 5 or 6 weeks, when many women are just finding out they are pregnant. As a test for when states can begin to ban abortions, this would effectively reduce the right to abortion to a right to take the morning-after pill.

Mississippi argues that by 15 weeks, the baby begins to be capable of feeling pain. But even if that were true, it wouldn’t provide a coherent basis for letting states ban the exercises of what the Court has identified as a fundamental right, since it’s a basic principle of our law that rights of that kind cannot be banned for the sake of a goal you could achieve without banning. And you can achieve the goal of preventing fetal pain by simply requiring fetal anesthesia before any abortion, as some jurisdictions do.

So, there is no legal source to cite for any new line between 0 and 15 weeks. The swing justices in Dobbs—Chief Justice Roberts and Justice Kavanaugh—will not want to reach a decision for which they cannot provide any lawyerly argument.

Might they instead rule for Mississippi without articulating a clear test?  I doubt it. This would guarantee endless re-litigation, keeping the Court in the political fray and the media spotlight. Every case upholding a more restrictive abortion law will be treated by the media as a full reversal of Roe and Casey all over again. If the Chief and Justice Kavanaugh are loath to bring the Court that kind of criticism unnecessarily, they will rather overturn Roe once than “overturn” it half a dozen times.

Besides, any new line the Justices drew in this case would actually make it harder for them to overturn Roe down the road. That’s because they’d have to justify any new line in Dobbs in their own voices, being unable to simply point to precedent or any other source. But having defended a residual abortion right in Dobbs, they’d have a hard time coming back in a future case to eliminate even that right. For then they’d be disagreeing not only with Casey and Roe but with their own words in Dobbs. That flip-flop on an intensely heated political issue would only further embarrass the Court.

If the Justices take the only sensible alternative to invalidating the law—by eliminating any constitutional entitlement to elective abortion—the procedure won’t suddenly be banned everywhere. It will simply be for the states to decide whether and how far to regulate or ban the procedure. So pro-life citizens will have to turn their efforts ever more toward state law reform and the support of women in difficult pregnancies. As the issue is taken out of the federal government’s hands, many single-issue voters will lose their main incentive for voting Republican for Congress and the White House, leading to a massive realignment of our partisan coalitions. As a culture, we will be forced to confront more deliberately and thoroughly than we have in 50 years the most searing questions of politics—questions of justice, life and death, and the duties and limits of good government. And you will be in college to see it.

Professor Sherif Girgis is an associate professor at Notre Dame Law School and a Rover faculty advisor.