Within hours of Maine Gov. Janet Mills publicly confronting President Donald Trump at the White House after he tried to bully her into complying with his administration’s ban on transgender athletes in women’s sports, the U.S. Department of Education launched a federal investigation into the state’s compliance with Title IX.

On Friday afternoon, the department’s Office for Civil Rights notified Maine Education Commissioner Pender Makin that it had opened an investigation into the Maine Department of Education and Maine School Administrative District #51. The probe focuses on the state’s policies allowing transgender students to compete in school sports, which OCR claims may violate Title IX protections for women’s sports, according to a department press release.

The move came after Mills stood up to Trump at the National Governors Association meeting Friday morning. Trump, singling out Mills during a televised press event, demanded that Maine comply with his executive order barring transgender athletes from competing in girls’ and women’s sports or risk losing federal funding.

“I’m complying with state and federal laws,” Mills responded.

Trump then said, “Well—I’m—we are the federal law. You better do it because otherwise, you’re not going to get any federal funding at all if you don’t.”

Mills, unfazed, replied: “We’ll see you in court.” Hours later, the governor’s office issued a press release in response to the newly announced investigation. Mills denounced the probe as political retaliation, warning that Trump is using federal power to punish states that refuse to comply with his agenda.

“No President—Republican or Democrat—can withhold federal funding authorized and appropriated by Congress and paid for by Maine taxpayers in an attempt to coerce someone into compliance with his will,” Mills said. “It is a violation of our Constitution and of our laws, which I took an oath to uphold.”

Related: Donald Trump bans transgender athletes from playing sports

She warned that Maine is only the first target.

“Who and what will he target next? Will it be you? Will it be because of your race or your religion? Will it be because you look different or think differently? Where does it end?” Mills asked.

She added, “In America, the President is neither a King nor a dictator, as much as this one tries to act like it – and it is the rule of law that prevents him from being so.”

LGBTQ+ advocates condemned the administration’s actions.

“Gov. Mills is standing up for all Maine students. HRC stands with Gov. Mills,” a Human Rights Campaign spokesperson told The Advocate.

Earlier in the day, Maine Attorney General Aaron Frey vowed to fight the investigation in court, calling it an “illegal and politically motivated attempt” to force the state into discrimination.

“Fortunately, the rule of law still applies in this country, and I will do everything in my power to defend Maine’s laws and block efforts by the President to bully and threaten us,” Frey said.

The White House and the Department of Education did not immediately respond to The Advocate’s request for comment.