On March 25, the Supreme Court will hear oral arguments in cases brought by for-profit companies that object to covering certain kinds of FDA-approved birth control for their employees, as mandated by the Affordable Care Act. Both corporations—Hobby Lobby and Conestoga Wood Specialties—say the contraception demand conflicts with their sincerely held religious beliefs. Namely, they believe life is sacred, that life begins when an egg is fertilized, and that some contraceptive pills and devices could endanger that life. “The mandate requires us in essence to become abortion providers,” Hobby Lobby President Steve Green told reporters last fall. “Our conscience does not allow us to do that.”

The medical establishment disputes this claim, even as the beliefs behind it cannot be as easily dismissed. In federal law and medical terms, pregnancy does not begin with a fertilized egg, but with a fertilized egg that has implanted in the uterus. The contraceptives in question—Plan B, Ella, copper and hormonal IUDs—do not cause abortions as the plaintiffs maintain, because they are not being used to terminate established pregnancies.

“You don’t have a pregnant woman until the egg implants in a woman and sticks,” said Susan F. Wood, a former director of the women’s health office at the Federal Drug Administration (FDA) and now a professor at George Washington University. “That’s what the medical world has long considered pregnancy. That’s what the FDA thinks of as pregnancy. And that’s what our society thinks of as pregnancy.”

But the owners of Hobby Lobby and Conestoga, along with likeminded believers who morally object to jeopardizing embryos, have moved the goal posts in terms of what constitutes a pregnancy—and therefore what constitutes an abortion. And to bolster their argument, they have one unlikely ally in science on their side: the FDA itself.

On each carton of Plan B One-Step, a widely used emergency contraceptive, is an FDA-approved drug label (PDF). It lists how the product might function, noting it “works mainly by preventing ovulation.” A bullet point reads, “It may also prevent fertilization … or attachment of a fertilized egg to the uterus (implantation).” This language is virtually identical to many oral contraceptive labels. But it’s this last point—regarding implantation—that spurred on the Hobby Lobby and Conestoga cases.

Religious conservatives often use the FDA label in talking points. The anti-abortion site LifeNews.com reported the “FDA’s own labeling” says Plan B and Ella may block implantation. The socially conservative Family Research Council pointed to the label in a policy paper (PDF) on defining pregnancy. In their filings, the Green family of Hobby Lobby and the Hahn family of Conestoga reference the FDA’s Birth Control Guide as proof of their claims about the products they oppose.

And yet, the FDA information may not be up-to-date. Many experts now say the FDA labels for Plan B and similar morning-after pills are not current with the most recent research. In some ways, they are holdovers from early birth control labels. “Those labels were developed back in the 1960s, listing all the possible ways birth control pills would work,” said Diana Blithe, who directs contraceptive development at the National Institutes of Health (NIH). “In subsequent years, we’ve learned a lot more about how birth control works.”

Since the FDA approved Plan B in 1999, repeated studies have shown the drug does not inhibit implantation. After The New York Times’ Pam Belluck investigated these findings in 2012, the NIH and the Mayo Clinic updated their websites to remove the implantation clause. In Europe, the label for the drug Norlevo, which is identical to Plan B, has already been changed to reflect the most recent research. And the International Federation of Gynecology and Obstetrics and the International Consortium for Emergency Contraception have issued statements saying levonorgestrel-only emergency contraceptives do not stop implantation.

This research means that Plan B and its equivalents do not meet even Hobby Lobby and Conestoga’s definitions of “abortion-inducing,” making part of their objections to the contraception mandate moot.

So why hasn’t the FDA updated its labels to clarify this? Spokeswoman Erica Jefferson could not comment on the Supreme Court litigation, but she wrote in an email that “the agency is aware of emerging data that suggests that levonorgestrel emergency contraception does not inhibit or prevent implantation of the fertilized egg.” She noted that it’s typically up to the company that makes the drug, not the FDA, to initiate a label change based on the latest science. Plan B-One Step’s manufacturer, Teva Pharmaceutical Industries, would have to make the request, which would allow generic makers to follow suit.

What’s holding the company back? After all, wouldn’t clearing Plan B’s name be good for business? A Teva spokesperson declined to comment, but it’s worth mentioning that Teva has previously asked the FDA to remove implantation from the label, and the agency declined. Plus, the application process for a label change can be expensive, and this update is unlikely to affect sales from women who need emergency contraception.

“We have to spend a lot of time and energy talking about how these products do and do not work, but we’ve been addressing a political concern, not a concern many woman have,” said Kelly Cleland, a researcher at Princeton’s Office of Population Research. “It’s a concern religious organizations and politicians have who are trying to restrict access to reproductive health services.”

The FDA could order label changes if a product’s dosage or safety was an issue. (It’s more likely that Teva will have to update Plan B’s label to include weight limits, which recent reports say could impair its effectiveness.) Even if morning-after pills prevented implantation, they would still work as intended: as safe contraception, not abortion pills. Indeed, according to Wood, the hormone in Plan B is so benign that it may be given to a woman in danger of miscarrying or delivering too early because it could help her keep the pregnancy.

Morning-after pills, though, are only one part of the debate. IUDs, also named in the Hobby Lobby and Conestoga suits, almost certainly can inhibit implantation. And less research has been done on Ella, the week-after pill, though data indicate it works like Plan B. It is this uncertainty that drives many religious objectors: they protest if there is any chance an embryo could be harmed.

Dr. Donna Harrison, who directs the American Association of Pro-Life Obstetricians and Gynecologists, stops short of calling Ella and IUDs abortifacients, but she does label them “embryocidal.” She wants more research on Plan B as well. “There are literally hundreds of interactions that have to happen for implantation to occur. If you test one or two, it is not definitive.” But testing for every possible interaction in pregnant women presents a host of ethical and logistical complications, too.

Rejecting birth control has traditionally been associated with the Catholic Church, whose hierarchy is largely consistent in its opposition to contraception. But the Southern Baptists who own arts and crafts retailer Hobby Lobby and the Mennonite woodworkers who own Conestoga are Protestants, and arguably less consistent in their objections. They do not, for example, refuse to cover birth control pills, many of which the FDA also warns could stop implantation. It would be more consistent, as some evangelicals have begun to do, to question all forms of oral contraception. Before filing a lawsuit condemning emergency contraception, Hobby Lobby was covering emergency contraceptive pills for employees, an oversight admitted during litigation.

Ultimately, the justices won’t decide these cases based on the plaintiffs’ inconsistent or consistent beliefs. The government has already acknowledged that the Greens’ and Hahns’ beliefs are sincere and deeply held and that their religious opposition is “not subject to questioning” in court. The real issue will be whether their religious exercise rights are substantially burdened, and whether corporations are entitled to religious rights at all. The court will not “inquire into the validity of a religious tenet.”

In the United States, you have the liberty to believe what you want—that the earth is 6,000 years old, that climate change is false, that abortion should be illegal—even if science or the law contradicts it. We know the Court’s decision will not settle contraception coverage entirely, just as Roe v. Wade did not end the abortion debate. Which is why we need the most up-to-date science—and for government entities to refute “abortion-inducing” misnomers. True, science can be a poor arbiter in religious arguments, but in the legal and rhetorical battles over contraception, we’re entitled to our own opinions, not our own facts. For the sake of women’s health, it would help us all if the FDA got the facts straight.