“Roe v. Wade,” Chief Justice William Rehnquist wrote in 1992, “stands as a sort of judicial Potemkin Village, which may be pointed out to passers-by as a monument to the importance of adhering to precedent. But behind the facade, an entirely new method of analysis, without any roots in constitutional law, is imported to decide the constitutionality of state laws regulating abortion.”

Rehnquist was dissenting in Planned Parenthood of Southeastern Pennsylvania v. Casey, the landmark case in which the court “reaffirmed” the “essential holding” of Roe. The word “reaffirm,” to a three-judge plurality, meant “completely rewrite.” Casey replaced Roe’s strict protection of choice as a “fundamental right” with a standard that no one can honestly claim to understand.

That vague standard—called the “undue burden” test—will be on the line this term. On Friday, the Court granted cert in a case called Whole Women’s Health v. ColeThe Fifth Circuit upheld a Texas law that would shutter 75 percent of the health facilities providing abortions in the state; the Court will now decide whether that law can stand.

Texas, in 2013, passed (over Wendy Davis’s memorable filibuster) a law called H.B.2. The statute imposed two new requirements on abortion facilities: First, doctors performing abortions must have “admitting privileges” at a hospital within 30 miles of the clinic, and, second, clinics must meet all the requirements for “ambulatory surgical centers” (ASCs). Those standards govern things like the width of hallways and other architectural features. It also can require expensive renovations to comply with, which may in fact be impossible to meet without finding or building a new structure.

The proceedings below have been long and complicated, but in essence the district court, after a trial, concluded that neither requirement was actually aimed at providing better health outcomes for patients. Patients at clinics can be, and regularly are, admitted to nearby hospitals when an emergency arises; there is, medical evidence suggested, no reason that the abortion provider be the doctor signing the admitting form. And the ASC standards were unnecessary to promote patient health. The state, the court noted, allows ASCs that don’t perform abortions to remain open even if they don’t meet the new standards; new ones must meet all the requirements known as a “grandfather clause.” But the state decided not to allow grandfathering of abortion clinics, instead requiring them to conform or close at once.

The net result of the new law would be the shuttering of three-quarters of the state’s clinics. The judge concluded that the law was aimed, not at promoting health, but at restricting the right to choose, and was thus an “undue burden.”

The Fifth Circuit reversed. A three-judge panel rebuked the district judge for examining the actual effect of the law. “All of the evidence referred to by the district court is purely anecdotal,” it said, “and does little to impugn the State’s legitimate reasons for the Act.” In essence, all that mattered was that the restrictions had something to do with health, and that the state said the requirements were aimed at promoting health.

If any vestige of the right to choose remains as an actual right—what Linda Greenhouse of The New York Times memorably called “a right like any other”—then the Texas law should be struck down. These regulations “relate to” health much the way the old Southern literacy tests “related to” the right to vote: In the guise of rules, they are prohibitions.

Yet the Court, without overruling Casey, could vote to strike down the Texas law or to allow it. That’s because no one knows what the “undue burden” means. Even in the world of law, where the meaning of words can sometimes delicately be called elusive, “undue burden” is distinctly and bizarrely vague.

For a definition, look to the Casey plurality: “A finding of an undue burden is a shorthand for the conclusion that a state regulation has the purpose or effect of placing a substantial obstacle in the path of a woman seeking an abortion” before the fetus is viable, a stage that now means roughly 24 weeks. Obstacles are okay—“the fact that a law which serves a valid purpose, one not designed to strike at the right itself, has the incidental effect of making it more difficult or more expensive to procure an abortion cannot be enough to invalidate it”—as long as it’s not “substantial.”  

Such obstacles, as “informed consent” provisions that have nothing to do with medical consent, are okay: The state “may express profound respect for the life”—unless those regulations pose a  “substantial obstacle.” The state can impose a waiting period designed to make a woman think really hard about whether she wants to do something the state doesn’t want her to do—unless the waiting period is a “substantial obstacle.”

I’ve been teaching Casey for 20 years, and I have no idea what that even says, much less means. We know a few things are “undue burdens.” Most prominent among them was a requirement, at stake in Casey, that a married woman, with a few exceptions, must notify her husband before having an abortion. The plurality dismissed this as giving the husband an “effective veto” over a woman’s choice. “A State may not give to a man the kind of dominion over his wife that parents exercise over their children,” the joint opinion said.

Perhaps not; but later cases have suggested that the government itself may have a kind of parental dominion over women. In a case called Gonzales v. Carhart, a majority of a different court—with Justice Samuel Alito replacing Sandra Day O’Connor—wrote that regulations may not be an “undue burden,” if they are designed to keep a woman from choosing a method of abortion she may regret later. “While we find no reliable data to measure the phenomenon,” Justice Antony Kennedy wrote blithely,  “it seems unexceptionable to conclude some women come to regret their choice to abort the infant life they once created and sustained.” Thus, some abortion procedures can be banned even if a doctor believes they are best for a woman’s health—as long as the law doesn’t totally ban abortion. Some obstacles, then, may be justified by nothing more than the state’s interest in protecting women from their own choices.  

Remember that the definition of “undue burden” originally said that the law has to serve “a valid purpose, one not designed to strike at the right itself.” If the court holds that the Texas law is not an “undue burden,” it will be hard not to conclude that “valid purpose” no longer has any meaning. As long as a state keeps a straight face, any kind of “health” regulation may be affirmed; and more aggressive restrictions—like the total bans on abortion after 20 weeks, much earlier than viability, passed by more than a dozen states in recent years—may also pass the “test.” These laws also “relate to” health—they rely on the untested claim that fetuses can feel pain at that stage. Pain is medical, even if medical opinion doesn’t support the rule. The “right” to choose may remain in place, growing smaller and smaller until, in practical terms, it disappears altogether. Casey, having devoured Roe, may now devour itself.

Or the court may enunciate a new test. I count four justices who would with a “rational basis” test—in essence, telling states that they can do pretty much whatever they want. That sort of plain speaking, though, is not congenial to Justice Anthony Kennedy, who joined the Casey “undue burden” test but who also wrote the later opinion proclaiming that women must be protected from themselves. He may not like to be called a “swing vote”; but let us, on this matter at least, speak plainly. In this case he is.

In 1992, the Casey plurality began its opinion this way: “Liberty finds no refuge in a jurisprudence of doubt.” Nearly a quarter century later, I read those words and don’t know whether to laugh or cry.