Last week, Sen. Rand Paul reintroduced his “Life at Conception Act,” an attempt to ban all abortion by granting legal “personhood” to zygotes and fetuses from “the moment of fertilization,” all without needing a constitutional amendment or Supreme Court decision overturning Roe v. Wade. Paul has been a staunch backer of such personhood efforts despite once claiming that he didn’t support “changing any of the laws” on abortion “until the country is persuaded otherwise.”

The bill Paul introduced last week varies slightly from the one he first introduced in 2013, specifically stating that it shouldn’t be construed as “a prohibition on in vitro fertilization, or a prohibition on use of birth control or another means of preventing fertilization.”

Personhood measures have been widely criticized for vague wording that could put legal birth control at risk, a concern that Paul appears to attempt to put at rest in the new bill. But that would all depend on what counts as protected birth control under the bill. Would IUDs, which could possibly prevent the implantation of a fertilized egg, be protected? What about the morning-after pill or hormonal contraception bills, which some anti-choice groups claim, with little evidence, could do the same thing? Some anti-choice activists claim that some or all of these constitute abortion, not birth control … notably the plaintiffs in the Hobby Lobby case, whose cause Paul enthusiastically supported.

It’s especially interesting that Paul attempts to avoid the growing controversy within the anti-abortion movement about in-vitro fertilization and the rights that should be granted to the excess frozen embryos that are often a byproduct of the process. It’s unclear if Paul is saying that embryos that are the result of in-vitro fertilization should not be granted the personhood rights that his bill would grant to all other embryos or if the bill would simply require that those embryos never be destroyed.

Both Paul’s 2013 bill and his 2016 version state that they shouldn’t “be construed to require the prosecution of any woman for the death of her unborn child,” an important exemption because under such a law, ending a pregnancy at any stage would be the legal equivalent of murder. Already, an experiment in personhood-style laws in Alabama has led to the arrests of hundreds of women for using drugs while pregnant or otherwise contributing to the “chemical endangerment” of a fetus.

All of this, of course, is purely hypothetical at this point. Paul’s bill is the product of a theory, which is controversial even within the anti-abortion movement, that there is a magic loophole in Roe v. Wade that would allow legal abortion to come tumbling down if Congress were simply to define fertilized eggs as “persons” under the law. Most likely, however, such a strategy would collapse in the courts: One prominent anti-choice attorney has called the personhood loophole an “urban legend.”

That’s not to say that Paul’s strategy doesn’t have support. His fellow Republican presidential candidate Mike Huckabee has been talking up the personhood strategy on the campaign trail, saying that he would simply issue a decree as president that there would be “no more abortion” in America. Ted Cruz has quietly pledged to support personhood measures and said late last year that a personhood strategy to avoid Roe would “absolutely” work. Marco Rubio has hinted at a personhood strategy, but not explicitly embraced it.

Paul’s bill has six Senate cosponsors and a similar bill (without the exceptions for birth control and IVF) has 132 cosponsors in the House.