WASHINGTON — A federal judge on Wednesday rejected President Trump’s latest effort to stop a lawsuit that alleges Trump is violating the Constitution by continuing to do business with foreign governments.

The ruling, from US District Judge Peter Messitte in Greenbelt, Md., will allow the plaintiffs in the case — the attorneys general of Maryland and the District of Columbia — to proceed with their case, which says Trump has violated the Constitution’s little-used emoluments clause.

The plaintiffs now want to interview Trump Organization employees and search company records to determine which foreign countries have spent money at Trump’s hotel in downtown Washington.

The Justice Department and Trump’s attorneys did not immediately respond to requests for comment. They could try to appeal the decision to a higher court and ask Messitte not to allow the attorneys general access to Trump Organization employees and books until the appeal is decided.

The lawsuit, filed last year by DC Attorney General Karl Racine, and Maryland Attorney General Brian Frosh, cleared an initial hurdle in March. Back then, Messitte settled one legal question, ruling that the plaintiffs had legal standing to sue the president in the first place.

He also limited the scope of the case to Trump’s Washington hotel; previously, the plaintiffs had also wanted to search for foreign-government spending at other Trump properties as well.

The next unsettled questions: What, exactly is an emolument?

That was a question that remained unanswered for more than 200 years.

The Constitution bars federal officials from taking emoluments from any ‘‘King, Prince, or Foreign State.’’ The Founding Fathers’ intent had been to stop US ambassadors overseas — emissaries from a new, poor, fragile country — from being bought off by jewels or payments from wealthy European states.

But the modern meaning of the clause had not been settled because most presidents — acting on the advice of their attorneys — had steered clear of business entanglements while in office.

Trump, on the other hand, has kept ownership of his business empire, including more than 10 hotels and golf clubs around the world. Although Trump has said he gave up day-to-day management of his businesses, he still owns them and can withdraw money from them at any time.

Some of his customers have been foreign governments. In particular, the Trump International Hotel on Pennsylvania Avenue in downtown Washington — just blocks from the White House — has rented out large ballrooms to the embassies of Kuwait and the Philippines and hosted visiting leaders from Malaysia and Romania.

At the hearing in June, the plaintiffs had argued that when applied in a modern context, the Constitution’s ban on emoluments should ban transactions such as those.

They said that emolument in this case should not just mean an outright gift but also any transaction that gave Trump ‘‘profit, gain or advantage.’’

But Justice Department attorneys, defending the president, said that this definition twisted the Constitution’s original meaning.