Pennsylvania Gov. Josh Shapiro sued the Trump administration on Thursday over its broad freeze of federal funding, saying in a lawsuit that the effort has “jeopardized at least $5.5 billion that has been committed to Pennsylvania” in federally appropriated money.

In the lawsuit, the Shapiro administration said Trump is in violation of the Administrative Procedure Act and conducting “an unconstitutional withholding of funds.” The law allows judges to throw out federal agency actions that are “arbitrary and capricious” on various grounds and has commonly been cited in lawsuits targeting elements of Trump’s efforts to rapidly remake the government.

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“Neither the President nor any executive branch agency has the power to unilaterally enact, amend, or repeal any statute. That is as true of a statute appropriating funds as it is any other statute,” the lawsuit reads, adding, “The President and executive branch agencies have an obligation to execute the laws that have been properly enacted. Defendant agencies’ withholding of appropriated, obligated funds violates these fundamental constitutional tenets and is therefore unconstitutional.”

The lawsuit, filed in the U.S. District Court for the Eastern District of Pennsylvania, is the Democratic governor’s most significant step to counter Trump so far in his second term. Shapiro is widely seen as a potential 2028 Democratic presidential candidate. That it was Shapiro himself suing the president, too, was notable because such a lawsuit would typically be filed by a state’s attorney general. In Pennsylvania, that office is now in Republican control.

The Shapiro administration sued the Interior Department, Transportation Department, Energy Department, Environmental Protection Agency and the Office of Management and Budget as well as the leaders of those agencies: Interior Secretary Doug Burgum, Transportation Secretary Sean Duffy, EPA Administrator Lee Zeldin, Energy Secretary Chris Wright and OMB Director Russ Vought.

“The federal government has entered into a contract with the Commonwealth of Pennsylvania, promising to provide billions of dollars in Congressionally-approved funding that we have committed to serious needs — like protecting public health, cutting energy costs, providing safe, clean drinking water, and creating jobs in rural communities,” Shapiro said in a statement. “With this funding freeze, the Trump Administration is breaking that contract — and it’s my job as Governor to protect Pennsylvania’s interests.”

Both in the lawsuit and in his statement, Shapiro framed his administration’s move on Thursday as a last resort that followed two weeks of trying to restore the frozen funding to his state.

“While multiple federal judges have ordered the Trump Administration to unfreeze this funding, access has not been restored, leaving my Administration with no choice but to pursue legal action to protect the interests of the Commonwealth and its residents,” he said.

A person familiar with the lawsuit told NBC News that the litigation was evidence Shapiro is willing to “go toe-to-toe with the president here and say ‘this is not a way to run government.’”

“This is not a vanity lawsuit [or] virtue signal,” this person said. “This is real. Things aren’t getting done. Key priorities of the governor’s agenda are close to pausing. There’s jobs at stake. There’s key initiatives in public health and human safety that are at stake.”

The White House did not immediately respond to a request for comment. Trump and his administration have argued for the funding freeze as necessary to root out what they see as wasteful and abusive, even fraudulent spending. But judges have said Trump lacks the authority to unilaterally pause the funds.

Much of the frozen federal funding Shapiro highlighted in his lawsuit stemmed from former President Joe Biden’s Infrastructure Investment and Jobs Act and Inflation Reduction Act, which was frozen under a Trump executive order that broadly called for funding appropriated by that legislation to be paused. The first paused-initiative Shapiro highlighted was a $3 billion grant over 15 years allowing Pennsylvania’s Department of Environmental Protection to repair abandoned mine lands in the state. Cleaning up abandoned mines was a major pledge of Shapiro’s 2022 gubernatorial campaign.

“It was a campaign promise — it’s a big deal,” the person familiar with the lawsuit said. “There’s [about] 300,000 orphaned and abandoned wells in the state of Pennsylvania. It’s like the second or third biggest emitter of greenhouse gasses. It’s a climate initiative. It’s a safety thing. It’s a union jobs. It’s mostly in western, rural Pennsylvania. This is 10s of millions of dollars up in the air of work that is struggling to proceed because no one has any idea what’s going on.”

Two federal judges have temporarily blocked the Trump administration’s funding freeze. But Shapiro’s lawsuit says that the federal government is continuing to withhold the funds to his state. 

“Specifically, Commonwealth agencies cannot draw from federal accounts, which means that agencies are stuck incurring debts and obligations in ongoing projects that cannot be reimbursed,” the lawsuit reads. “While agencies have some reserves and discretionary dollars to cover small unexpected debts, the scope of the federal freeze will far exceed those reserves.”