For people who care about abortion rights, these are worrying times.

Of course, pro-choice advocates began losing sleep the minute Donald Trump was elected. During the 2016 presidential election, Trump claimed that Roe v. Wade – the 1973 landmark decision establishing that women have a constitutional right to access abortion – would be “automatically” overruled by his Supreme Court picks.

Shortly after taking office, Trump announced his first Supreme Court nominee, the conservative Neil Gorsuch, who replaced the conservative Justice Antonin Scalia. Swapping one conservative for another didn’t change much for Roe. But now, a second spot has opened up on the court with the retirement of Justice Anthony Kennedy – who has been a key vote to preserve abortion rights.

From my vantage point as a constitutional law professor who also litigates reproductive rights cases, the future of Roe v. Wade looks more tenuous than it ever has.

A new vacancy, a new court

Replacing Kennedy with a more conservative judge could fundamentally remake constitutional doctrine in this area.

In 1992, Justice Kennedy was a swing vote to preserve Roe v. Wade in a 5-4 decision known as Planned Parenthood v. Casey. More recently, in the 2016 case of Whole Woman’s Health v. Hellerstedt, Justice Kennedy’s vote was critical to the five-justice majority, which again affirmed the right to choose as fundamental.

But Justice Kennedy’s proposed successor Brett Kavanaugh has expressed hostility to Roe. In a public speech last year, Kavanaugh praised the late Chief Justice William Rehnquist’s dissent from the Roe decision. He also voted against an undocumented minor in government custody who wanted an abortion, complaining that the judges who voted in favor of the young woman were granting a right to “abortion on demand” and arguing that the woman should have to delay the procedure for a few weeks until she could be placed with a family. This record suggests Kavanaugh could provide a critical fifth vote to the anti-Roe wing of the court, joining Justices Clarence Thomas, John Roberts, Samuel Alito and Gorsuch.

What happens if Roe is overruled?

If the Supreme Court votes to overrule Roe, it wouldn’t immediately make abortion illegal throughout the country. That would probably require five justices to decide that embryos and fetuses are “persons” entitled to constitutional protection. No justice – not even Scalia – has ever taken such an extreme view.

Instead, the court would probably say that states are allowed to restrict abortion however they see fit. It would say that states can choose to protect potential life, and that the woman’s right to choose whether and when to become a parent is not strong enough to overcome the state’s interest in protecting fetuses.

That means some states would probably outlaw abortion altogether, perhaps with narrow exceptions in cases or rape or incest, or when the woman’s life is in danger. Other states may place few or no restrictions on abortion – perhaps making it illegal only once the fetus is viable, typically after the 22nd week of pregnancy.

The role of Roberts

Of course, it’s possible that Roe will live another day.

With Kennedy gone, Chief Justice John Roberts will be at the ideological center of the Court, with four conservatives – Thomas, Alito, Gorsuch, and Kavanaugh – all to the right of him. Roberts is therefore likely to become the swing vote.

Roberts is a famously careful jurist who often avoids overruling precedent if he can do so by issuing a narrow opinion instead. He is also likely concerned about his legacy. He might not want the Roberts court to be the court that overruled Roe and took away the right to choose. He might be concerned about the backlash among members of the public, who have long assumed that Roe was here to stay and who favor keeping it by more than a two-to-one margin.

Then again, many justices have affirmed their devotion to precedent, only to later overturn it. Both Roberts and Gorsuch spoke favorably about following precedent during their Senate confirmation hearings. Yet both justices voted just this past term to overturn a unanimous Supreme Court case protecting the rights of unions – Abood v. Detroit Board of Education – that had stood undisturbed for more than 40 years.

A challenge in the states

Also, importantly, numerous states stand ready to mount a challenge to Roe. In 2018 alone, seven states have introduced or passed so-called “heartbeat bills” that ban abortion as early as six weeks of pregnancy. But the Supreme Court doesn’t need to consider a challenge to a heartbeat bill in order to overturn Roe.

In fact, the Supreme Court gets to pick and choose the cases it hears and needs only four justices to vote to hear a case. That means it might decide to weigh in on abortion rights as soon as its next term. Almost any case, including several that are already pending, could become a vehicle for overturning Roe.

For example, the newly composed Supreme Court could decide to take up the constitutionality of laws in Ohio or Indiana banning abortions sought for particular reasons, such as fetal anomaly. Both laws have been blocked by federal courts, and either could still be appealed to the Supreme Court. If the court decides to hear one of those cases, it could uphold the laws on the grounds that Roe was incorrect and a new, more relaxed legal standard should apply to abortion restrictions.

What’s more, 10 states including Wisconsin and West Virginia, actually still have pre-Roe abortion bans on the books. These laws weren’t being enforced as long as Roe was the law of the land. If Roe is overturned, it’s possible that prosecutors in those states would try to bring criminal charges against doctors performing abortions, without even waiting for the legislature to pass a new law banning abortion.

Four additional states – North Dakota, South Dakota, Louisiana and Mississippi – have passed so-called “trigger laws” providing that abortion will become illegal the moment Roe is overruled.

Even in the absence of laws such as these, though, many state legislatures won’t hesitate to enact new abortion bans immediately. In fact, the Center for Reproductive Rights considers only 19 states to be relatively low-risk for passing new abortion bans if Roe fell.

Of these 19, a few states are expected to take an active role in protecting abortion access in the absence of Roe. This means that women in Massachusetts continuing to have one set of laws, and women in Mississippi will have a very different set.

Still, it’s important not to lose sight of the bigger picture. Whether or not Roe goes, the Supreme Court is likely to shift far to the right on reproductive rights — potentially affecting not just abortion, but access to contraception as well. One sign of this shift is Kavanaugh’s record of siding with employers seeking to block employees’ access to birth control under the ACA.

And, even if Roe isn’t overturned, it may continue to exist in name only, as the Supreme Court is likely to uphold every sort of restriction short of an outright abortion ban.

In short, there are many possible paths for Roe v. Wade in the future, and significant questions remain. One thing is almost certain, though – the court will continue to erode the power of Roe.

This story has been updated from a version that originally ran on March 19, 2017.

B. Jessie Hill receives funding from an anonymous foundation that supports research on reproductive health care. She is a volunteer attorney for the ACLU of Ohio and litigates challenges to abortion restrictions.