Georgia sued the Obama administration Wednesday over a directive to public schools over transgender bathroom rules, joining a group of 11 states challenging the federal government over the controversial guidelines.

It was a surprising move from state leaders, who last week blasted the guidance that directed public schools to allow transgender students to use bathrooms that match their gender identity as a "federal overreach" but stopped short of endorsing a lawsuit.

Attorney General Sam Olens said Wednesday, though, that Georgia was compelled to act because of the implicit threat that the federal government could withhold funding from schools if they refuse to comply with what he called a “legally unsound mandate.”

“The guidance letter is yet another example of the president’s unconstitutional overreach,” Olens said. “The Constitution gives only Congress the power to write and rewrite laws.”

Obama’s guidance was released days after the U.S. Department of Justice and North Carolina filed near-simultaneous lawsuits over the state law that requires transgender people to use the public restroom at schools and other public places that matches the sex on their birth certificates.

The directive is not a mandate and does not carry the force of law, but schools that ignore it could potentially lose federal funding. The federal government provides about $2 billion a year to Georgia in k-12 education funding.

Several Georgia districts have signaled they would comply, though state Superintendent Richard Woods said he had “safety and privacy concerns” about the new policy.

The lawsuit was filed after a majority of state Senate Republicans and others urged Gov. Nathan Deal and Olens to file a legal challenge to block the directive and also assure local school systems that the state would defend them in court if they defied it.

Already, some conservative lawmakers are planning legislation next year that would allow parents to sue the state and their school district if their child is “victimized” in a bathroom because of the directive. They worry that the measures are needed to protect students and others from sexual predators.

“It’s a naked power grab by the Obama administration. States should not simply acquiesce when the president issues some sort of decree and threatens to take money away from schools,” said state Sen. Josh McKoon, among the Republicans who urged Olens to take action. “It’s clearly illegal, and this is what you should do when you’re confronted with something that’s clearly illegal.”

Critics said Georgia will end up on the wrong side of history by challenging civil rights protections for a minority group. And they say the threat is overblown.

“Transgender students are the most vulnerable children in our schools,” said Robbie Medwed, the education director of the Southern Jewish Resource Network for Gender and Sexual Diversity. He said Olens is fighting to protect “the mistreatment of at-risk and vulnerable children who are simply trying to learn and grow.”

The lawsuit, filed in a Texas federal court, claims the Obama administration “conspired to turn workplaces and educational settings across the country into laboratories for a massive social experiment, flouting the democratic process, and running roughshod over commonsense policies protecting children and basic privacy rights.”

The other states participating in the suit are Alabama, Arizona, Louisiana, Maine, Oklahoma, Tennessee, Texas, Utah, West Virginia and Wisconsin.

The suit could set a legal precedent over whether federal civil rights protections extend to transgender people and further define how the executive branch can use its powers to coerce states into making decisions. Tara Borelli, a senior attorney with the gay rights group Lamba Legal, said the lawsuit puts Georgia on an “incredibly disappointing” path.

“They are not on the side of all students when they take a step like this,” she said. “This isn’t about equal respect for all students. And it’s important that schools support all students, including transgender students.”