A federal judge on Monday said lawyers for Maryland and Washington, D.C., can begin issuing subpoenas in a lawsuit that accuses President Donald Trump of using his luxury hotel in Washington to unconstitutionally profit from his political office.

The attorneys general in Maryland and Washington say they plan to serve as many as 20 companies and government agencies with subpoenas by midday Tuesday. It’s the first time a lawsuit alleging a president violated the Constitution’s emoluments, or anti-corruption, clauses has advanced to the discovery stage.

A similar suit against Trump brought by Democratic lawmakers cleared an initial hurdle in federal court in Washington, while a pair of suits filed in New York were thrown out by a judge there. That decision is on appeal. None of those cases has proceeded to the discovery stage yet.

The Justice Department on Friday said it would try to halt the attorneys general case with an appeal to the 4th Circuit Court of Appeals in Richmond, but by Monday night, it had yet to file anything in that court. The department said it plans to seek a writ of mandamus, a process that would halt the legal proceedings as illegal or improper.

A DOJ spokeswoman declined to comment on the decision Monday. There was no immediate word on when the 4th Circuit appeal would be filed.

Subpoenas will be issued to state and federal government agencies and to customers and competitors of the Trump International Hotel, located just down the street from the White House, Maryland Attorney General Brian Frosh said. If Justice Department lawyers do seek to stop the case, he said he was confident the delay would be temporary.

“They have a very high burden to win on a writ of mandamus, I don’t think they can meet that standard here,” Frosh told POLITICO. “They’ve done everything they possibly can to stop us from getting discovery.”

D.C. Attorney General Karl A. Racine called the Constitution‘s emoluments clauses “our nation’s original anti-corruption laws.”

A spokeswoman from the Trump Organization, Amanda Miller, did not respond to a request for comment. The White House did not immediately respond to a request for comment.

The suit, filed in June 2017, accuses Trump of violating two emoluments clauses of the Constitution, which limit the president’s ability to receive financial benefits from states and foreign governments.

The Trump Organization says it is donating to the U.S. Treasury profits from hotel business with foreign governments, but it hasn’t explained how those amounts are calculated.

Judge Peter J. Messitte, who was appointed by President Bill Clinton, rejected earlier arguments from Justice Department attorneys that Maryland and D.C. lacked legal standing to pursue the emoluments case. He also ruled against Trump’s lawyers’ argument that the emoluments clauses exclude private business transactions. Last month, he denied Trump’s request for an appeal in the case.

Lawyers from Cohen Milstein, Gupta Wessler, and the nonprofit Citizens for Responsibility and Ethics in Washington, or CREW, are assisting Racine and Frosh on the litigation.