Texas Attorney General Ken Paxton has filed a lawsuit against a Dallas-based pediatrician, accusing her of providing transition-related hormones to nearly two dozen minors in violation of a state ban on gender-affirming care for people under age 18.

In what the Republican described as the state’s first enforcement action under Senate Bill 14, the lawsuit seeks an injunction against May Lau, an associate professor of pediatrics at the University of Texas Southwestern Medical Center, who specializes in adolescent medicine at Children’s Medical Center Dallas.

The lawsuit accuses the physician of prescribing testosterone to 21 teenagers between the ages of 14 and 17 “for the purposes of transitioning their biological sex” from female to male.

Lau and the UT Southwestern Medical Center did not immediately respond to requests for comment, while Children’s Health said in a statement that it “follows and adheres to all state health care laws.”

Senate Bill 14, which went into effect in September 2023, prohibits health-care professionals from treating anyone under the age of 18 with gender-transitioning interventions such as surgeries, puberty blockers and hormones. Physicians found in violation of the law, which was upheld by the Texas Supreme Court in June, can lose their medical licenses.

“Today, enforcement begins against those who have violated the law,” stated the lawsuit, which was filed Thursday.

Paxton said in a statement Thursday, “Doctors who continue to provide these harmful ‘gender transition’ drugs and treatments will be prosecuted to the full extent of the law.”

While critics of gender-affirming treatment have long argued that children are too young to make the decision to medically transition, a number of studies on puberty blockers have found that transgender youth treated with medications showed lower rates of depression and anxiety.

The ACLU had sought to block Senate Bill 14. After the court upheld the law in June, the ACLU said the ban on gender-affirming care “threatens the health and lives of Texas transgender youth, and penalizes physicians who provide the best standard of care for their transgender patients.”

On Thursday, the ACLU said in response to the lawsuit filed against Lau that doctors “should not have to fear being targeted for providing health care to their patients,”

The lawsuit accuses Lau of “misleading” pharmacies and insurance providers by claiming that the testosterone she prescribed to her patients were for conditions unrelated to gender transition. In addition to an injunction, the lawsuit seeks penalties of up to $10,000 per violation.