Thanks to North Carolina, major legal questions about how civil rights law applies to transgender people will be hashed out in a case about their access to bathrooms.

“Transgender rights still are very much an open question in American law,” Adam Winkler, a constitutional law professor at UCLA, told TPM. “It’s going to take a law like the North Carolina bathroom bill to bring the question of transgender rights to the courts for final resolution.”

The Department of Justice and the state of North Carolina both announced Monday that they were taking their battle over an anti-LGBT law to the court. The feds and Republican Gov. Pat McCrory each filed their own legal complaints asking federal courts to weigh the legality of the state legislation known as HB2. The lawsuits announced Monday join a third lawsuit that was filed by a private LGBT rights group challenging the North Carolina law.

At the heart of the showdown is whether the bill’s bathroom provision — which prohibits trans people from using the bathrooms in government buildings and public schools that match their gender identity — is a violation of civil rights laws that bar discrimination based on one’s sex.

The dueling lawsuits could prove to be a history-making moment. Since the Supreme Court legalized same-sex marriage, the next frontier in LGBT law is the rights of transgender people, and the North Carolina ruling sets the stage for what could be a landmark ruling.

The Justice Department is suing the state in its capacity as an employer, alleging that implementing HB2 will discriminate against transgender state employees. The Justice Department specifically targeted the University of North Carolina and the state Department of Public Safety. Its continued threats to withhold federal funding from the university and law enforcement suggest the Obama administration is pulling no punches when it comes to blocking the law.

In press conference Monday announcing the DOJ lawsuit, Attorney General Loretta Lynch called the legislation “state-sponsored discrimination against transgender individuals, who simply seek to engage in the most private of functions in a place of safety and security – a right taken for granted by most of us.”

“We see you. We stand with you. We will do everything we can to protect you going forward,” Lynch vowed in her press conference, speaking directly to transgender Americans.

HB2 was rushed through the North Carolina state house in March as other state legislatures mulled and ultimately abandoned similar bills, for fears of legal sanctions and/or public relations nightmare. At the time, it was called one of the most anti-LGBT laws passed by a state legislature, and the feds have now made clear they don’t intend to sit on the sidelines.

“So long as there’s a Democrat in the White House, you can expect this case to continue on until there’s a final ruling on the merits, likely by the court of the appeals, possibly by even the Supreme Court,” Winkler said.

For years, the Obama administration’s own agencies have been treating trans discrimination like sex discrimination, which was outlawed by the Civil Rights Act.

The Department of Justice warned North Carolina as much in letter sent to the state last week. The feds told the state it had until Monday to back down on enforcing before the law. Rather than acquiesce or do nothing, McCrory escalated the battle on his own by filing a legal complaint accusing the Obama administration of a “radical reinterpretation” of the Civil Rights Act.

In a press conference Monday, McCrory called on other states and parties to join him, while framing the issue as an example of Obama administrative overreach.

“I anticipate our own legislature, other private sector entities from throughout the United States and possibly other states to join us in seeking this clarification because this is not just a North Carolina issue, this is a national issue,” McCrory said.

Hours later, the DOJ responded with a lawsuit of its own.

“This action is about a great deal more than bathrooms,” Lynch said. “This is about the dignity and the respect that we accord our fellow citizens and the laws we as the people and as a country have enacted to protect them, indeed to protect of all of us.”

Legal experts, citing a recent transgender rights case in Virginia, say McCrory has an uphill battle, and that it is telling what his complaint leaves out, not just what it charges.

“It’s sort of a skimpy complaint, considering all the issues involved, and when you look at the cases they cite, there’s very little recent and of course they don’t cite the stuff that goes against them,” said Arthur Leonard, a professor at New York Law School and editor of LGBT Law Notes, which tracks legal developments in that area of law.

Notably the lawsuit filed by McCrory makes no mention of Title IX, one of the federal statutes the DOJ says HB2 violates. Last month, the 4th U.S. Circuit Court of Appeals said Title IX was applicable in a lawsuit in Virginia where a transgender teenager is suing his school for not allowing him to use the men’s bathroom.

The DOJ lawsuit, meanwhile, calls the HB2 a violation of both Title VII and Title IX of the Civil Rights Act, as well as the Violence Against Women Act.

In addition to the 4th Circuit ruling in the Virginia case, there are other signs that federal courts are trending towards the Obama administration’s understanding of how anti-sex discrimination laws apply to trans rights. A 2008 federal court decision invoked Title VII when siding with a transgender woman whose job offer with the Library of Congress was rescinded because she was transitioning. A panel of the 11th Circuit of Appeals also said transgender discrimination amounted to sex discrimination in a 2011 case where a Georgia General Assembly transgender employee had been fired because of her gender identity.

“Many people in LGBT community would hope the North Carolina would just give in, but there is a silver lining for the LGBT community,” Winkler said. “The silver lining is that their rights will never be fully secure until we have authoritative rulings by the federal courts giving them those protections. The fight between North Carolina and the federal government over bathroom access promises to be one of those cases that leads to authoritative rulings about the scope of transgender rights.”