On Tuesday, the U.S. Supreme Court examined restrictive abortion legislation in Indiana, in particular a portion of the state’s law that prevents abortion based solely on the fetus’ sex, race or disability. While the Court didn’t issue a ruling on this portion of the law (on the grounds it needs to appear before other Courts of Appeal), Justice Clarence Thomas penned a multi-page concurring opinion linking abortion to eugenics.

Thomas wrote, “This law and other laws like it promote a State’s compelling interest in preventing abortion from becoming a tool of modern-day eugenics. Technological advances have only heightened the eugenic potential for abortion, as abortion can now be used to eliminate children with unwanted characteristics, such as a particular sex or disability.”

In a statement to CNN, a Planned Parenthood official said, “We denounce eugenics in all forms for the same reason we are working to fight abortion bans across the country.”

The late Margaret Sanger, who founded the organizations that would become Planned Parenthood, wrote openly about eugenics. She stated she believed “in the sterilization of the feeble-minded, the insane and syphilitic” and said “there should be no children when either mother or father suffers from such diseases as tuberculosis, gonorrhea, syphilis, cancer, epilepsy, insanity, drunkenness and mental disorders.”

Explaining the reasoning for his lengthy opinion, Thomas wrote, “the use of abortion to achieve eugenic goals is not merely hypothetical.” As to why the Supreme Court deferred their opinion until more courts could weigh in, he said: “Given the potential for abortion to become a tool of eugenic manipulation, the Court will soon need to confront the constitutionality of laws like Indiana’s. But because further percolation may assist our review of this issue of first impression, I join the Court in declining to take up the issue now.”