Attorney General Pam Bondi speaks at a news conference Wednesday at the Justice Department. Ben Curtis/Associated Press

U.S. Attorney General Pam Bondi on Tuesday threatened to sue Maine if Gov. Janet Mills refuses to comply with President Donald Trump’s executive order calling for a nationwide ban on transgender student-athletes.

Bondi said in a letter that if federal investigations show that Maine is “denying girls an equal opportunity to participate in athletic events by requiring them to compete against boys, the Department of Justice stands ready to take all appropriate action to enforce federal law.”

“Maine should be on notice,” Bondi wrote. “I hope it does not come to this. The Department of Justice does not want to have to sue states or state entities, or to seek termination of their federal grants.”

Meanwhile, officials in Maine and in other states targeted by Bondi are pushing back, arguing that the executive order does not override state laws protecting the rights of transgender athletes.

Neither Mills’ office nor Attorney General Aaron Frey responded to questions about the letter Wednesday. On Tuesday, Mills, who has objected to the administration’s widespread attempts to use federal funding to coerce changes in state laws or policies, ignored questions from reporters as she returned to her office after attending the State of the Judiciary address before a joint session of the Legislature.

The letter from Bondi comes after Mills stood her ground when called out by Trump during an event with other governors at the White House last week.

Trump asked Mills if she planned to comply with his executive order, the stated purpose of which is “keeping men out of women’s sports.” Mills said she’d follow federal and state law, the latter of which prohibits discrimination based on gender identity, promoting Trump to say that “we are the federal law” before issuing a threat.

“You’d better do it,” Trump said. “You’d better do it, because you’re not going to get any federal funding at all if you don’t.”

“See you in court,” Mills replied.

The administration has now launched three investigations into whether Maine is allowing transgender athletes to compete in violation of the federal Title IX law, which expands opportunities for women in sports.

Maine Gov. Janet Mills disagrees with President Donald Trump as he speaks about transgender women in sports during a meeting of governors at the White House on Friday. Jabin Botsford/The Washington Post

The Department of Education’s Office for Civil Rights is investigating the state education department and the Cumberland-North Yarmouth school district. And the U.S. Department of Agriculture is investigating the University of Maine.

On Thursday, Craig Trainor, the acting assistant secretary of civil rights for the U.S. DOE, issued a public statement criticizing Mills, even as the investigation is ongoing.

“It is shameful that Governor Mills refuses to stand with women and girls,” Trainor said. “Her rejection of the antidiscrimination obligations that Maine voluntarily accepted when it agreed to receive federal taxpayer dollars is unlawful. OCR is still actively investigating Maine and one of its school administrative districts for apparent violations of federal law.

“To Maine education leaders who stand up for girls and will comply with Title IX in their school districts and campuses: The Trump administration—and the American people — support you fully.”

Maine’s policy on transgender student athletes was thrust into the national spotlight after Rep. Laurel Libby, R-Auburn, posted a photo on social media of a transgender student at Greely High School who won a state title, showing the athlete’s face and calling out the school district.

Libby was censured by House Democrats on Tuesday night. She will not be able to speak or vote on the House floor until she formally apologizes, which on Tuesday night she said she did not plan to do.

Bondi took issue with Mills’ written statement released after her White House interaction that said “Maine law has addressed” the issue and suggested that Trump was acting like a dictator. Bondi said federal law supersedes state law.

“It therefore does not matter if Maine state law allows, or even requires, state athletic associations or other similar entities to require girls to compete against boys in sports and athletic events,” Bondi said. “Where federal and state law conflict, states and state entities must follow federal law — not because we live in a dictatorship but because the Constitution requires states to follow the supreme law of the land.”

However, Dmitry Bam, a professor at the University Maine School of Law, questioned whether a reinterpretation of a federal law by an incoming administration would have the force of overriding state law. He said a president cannot impose his own conditions on federal grant funding and has no legal authority to withhold all federal funding to coerce a state into adopting a certain policy.

The issue will likely be determined in the courts.

On Tuesday, Valerie Stanfill, chief justice of the Maine Supreme Judicial Court, declined to comment on whether an executive order from the president had the power to override state law.

“I can’t really weigh in on that,” Stanfill said during a news conference following her State of the Judiciary speech, where she touched on the importance of the constitution’s separation of powers. “I think those are things that are going to have to be played out out and in fact could end up in some cases coming before us.”

Maine is one of 25 states without a law restricting transgender students from participating in sports consistent with their gender identity, according to the Movement Advancement Project, a nonprofit, LGBTQ think tank.

But Maine is only one of three states to receive a letter from Bondi. Similar letters were sent to California and Minnesota, where Title IX investigations are already underway.

In letters to California and Minnesota, Bondi said their states were among those whose athletic associations issued “defiant statements saying that they would continue requiring girls to compete against boys in sports and athletic events. ”

In Minnesota’s letter, she pointed to a four-page legal opinion issued by the state’s attorney general saying that complying with the executive order would violate state law.

“The Executive Order does not have the force of law and therefore does not preempt any aspect of Minnesota law,” Keith Ellison wrote. “Complying with the Executive Order and prohibiting students from participation in extracurricular activities consistent with their gender identity would violate the (Minnesota Human Rights Act).”

Ellison argued that the executive order does not “have the force and effect of laws” to supersede his state’s human rights act, because it has not been approved by Congress.

“Title IX does not authorize the president to issue directives with the force of law or to unilaterally rescind all federal funds from all educational programs that do not comply with presidential policy preferences,” he wrote.