WASHINGTON — A federal judge refused on Tuesday to halt a lawsuit by congressional Democrats alleging that President Trump has illegally profited from his business while in office, and ordered evidence gathering to begin on Friday.
The Justice Department said it would appeal the ruling by Judge Emmet G. Sullivan of United States District Court for the District of Columbia. Many legal experts predict that the extraordinary contest over whether Mr. Trump has violated the so-called emoluments clauses of the Constitution will eventually reach the Supreme Court.
The president’s lawyers had asked Judge Sullivan to delay the lawsuit, which was filed by nearly 200 congressional Democrats, while they appealed his earlier rulings to the United States Court of Appeals for the District of Columbia Circuit. But in a 12-page opinion, Judge Sullivan said the president had failed to meet the high standard required to put aside the usual procedure of appealing a judicial decision at the end of a case.
The Justice Department, he wrote, failed to prove that appealing his decisions might well end the litigation, one of three requirements to grant such a request. In fact, he wrote, the president’s lawyers “made little effort” to demonstrate that the lawsuit would be over if a higher court reviewed his rulings.
He also said that the burden placed upon the president to produce documents was far less onerous than other cases cited by the president’s lawyers. The entire process, he wrote, should conclude in about three months.
A Justice Department spokeswoman attacked the judge’s ruling, saying: “This case should have been dismissed. It presents important questions that warrant immediate appellate review and is another impractical attempt to disrupt and distract the president from his official duties.”
The case before Judge Sullivan is one of two now before federal courts, and his ruling could ensure that two separate appeals court panels will be reviewing the question of whether Mr. Trump has violated anti-corruption prohibitions in the Constitution. The lawsuits raise the constitutional issue — never before litigated until Mr. Trump took office — of what constitutes an illegal benefit, or emolument, to a federal official.
In the other case, brought by the District of Columbia and the State of Maryland, the Justice Department appealed adverse decisions by Judge Peter J. Messitte of Federal District Court in Greenbelt, Md. The department successfully sought a review of Judge Messitte’s decisions by a three-judge panel of the United States Court of Appeals for the Fourth Circuit in Richmond, Va.
Judges on that panel appeared sympathetic to the president’s arguments but have yet to issue a decision.