Abortion foes in state legislatures seem awfully sure of themselves lately. By passing bills that would severely restrict abortion, lawmakers in Alabama and Georgia have in effect asked the Supreme Court not only to overturn Roe v. Wade immediately, but also to recognize the personhood of the fetus. The history of the abortion debate suggests, though, that by going as far as these measures do, anti-abortion legislators may have overplayed their hand.

Start with the idea of fetal personhood. Both the Alabama and Georgia measures rely on the concept of “natural law”— unchanging moral principles that have supposedly existed since before the Constitution — to support the idea that a fetus is a person. But these kinds of arguments don’t have a record of judicial success.

Natural law-based arguments for fetal personhood were pursued by anti-abortion scholars and jurists for much of the 1960s and 1970s to little avail. These anti-abortion scholars avoided originalism, the prevailing conservative approach to constitutional interpretation, and instead focused on rebuking the Supreme Court for not recognizing the fundamental right to life that would have made all abortions illegal, including in the Roe case.

By the early 1980s, abortion foes generally gave up on this strategy. That’s because neither judges nor many other conservative lawyers, it seems, felt fully comfortable with recognizing rights not detailed in the text or history of the Constitution. After all, conservatives had long invoked the specter of judicial activism in criticizing their liberal colleagues, including those who issued the Roe decision.