President Trump is the target of a lawsuit filed Tuesday by the Democratic-led House of Representatives, seeking to force the Treasury Department to turn over Trump’s tax returns.

The action moves the months-long dispute between the House Ways and Means Committee and the Trump administration into the federal courts.

“The outcome is likely to determine whether financial information that Mr. Trump — breaking with longstanding tradition — has kept closely guarded as a candidate and as president will be viewed by Congress and, ultimately, by the public,” reports the New York Times.

Defendants named in the suit are Treasury Secretary Steven Mnuchin and IRS Commissioner Charles Rettig, who have denied Democrats’ demands and subpoenas for the returns.

“This is a big deal that goes to the core of our government’s checks and balances, and could for many years shape the relationship between the executive and legislative branches,” said Steven Rosenthal, a legal expert at the Tax Policy Center, a nonpartisan think tank, told the Washington Post.

“House Democrats and legal experts have pointed to a 1924 law that explicitly gives lawmakers the authority to seek the records,” the Post says, but the Trump administration has characterized the action “a partisan maneuver” to embarrass him and his supporters.

“While the fight over Trump’s taxes could be lengthy, with the administration likely to try to drag out the proceedings beyond next year’s elections, some see signs the courts are trying to move quickly on the oversight challenges,” says Politico.