Close-up image of the U.S. Congress

Last fall, when a Chinese scientist announced that he had created genetically modified twin babies, the world was stunned and outraged. In the U.S., we were able to draw some modicum of reassurance from a policy that has served as a barrier to such reckless human experimentation: A rider to the federal spending bill bars the Food and Drug Administration (FDA) from considering clinical trials “in which a human embryo is intentionally created or modified to include a heritable genetic modification.”

Yet now that provision is being eyed for removal.

When it was adopted in 2015, the provision brought the U.S. into closer alignment with most other countries across the globe with developed biotech sectors. During the late 1990s and early 2000s, dozens of national legislatures debated whether new genetic technologies should be used to alter the biology and traits of future human beings.

Every one of them decided that the benefits would be dubious at best and the societal dangers unacceptably dire, and passed laws against it. In Europe, 29 countries also signed and ratified the...