U.S. District Judge Daniel Domenico said in an opinion on Saturday that a Colorado law banning so-called medication abortion reversal treatment likely violates the U.S. Constitution’s guarantee of religious freedom. His order stops the state from enforcing the law against Bella Health and Wellness, which sued to block it, or against anyone else working with Bella Health, while he considers the medical center’s challenge to the law.

The office of Colorado Attorney General Phil Weiser, which defended the law, declined to comment.

Medication abortion begins with the drug mifepristone, which blocks the action of the hormone progesterone, crucial for sustaining pregnancy, and is completed with a second drug, misoprostol. Proponents of the so-called medication abortion reversal say that if a woman changes her mind after taking mifepristone but before taking misoprostol, the pregnancy can be continued by administering a high dose of progesterone.

There are no large controlled studies of the treatment, and the American College of Obstetricians and Gynecologists has said that its safety and efficacy are unsupported by science.