Donald Trump, accompanied by, from left, Eric Trump, Tiffany Trump, Melania Trump and Ivanka Trump, prepares to cut a ribbon during the grand-opening ceremony of the Trump International Hotel in Washington on Oct. 26. (Jabin Botsford/The Washington Post)

On Monday morning, a liberal watchdog group filed a lawsuit against President Trump, alleging he’d violated a previously obscure provision in the Constitution, the “Emoluments Clause.”

The watchdog group, Citizens for Responsibility and Ethics in Washington, said that the clause prohibits Trump-owned businesses from accepting payments from foreign governments.

They asked a court to stop Trump’s businesses from taking them now.

“This cannot be allowed,” the group wrote in its legal complaint.

[Watchdog group sues Trump, alleging he violated constitutional ban]

(Jenny Starrs/The Washington Post)

Trump called the case “totally without merit” during an event at the White House on Monday.

Even if this case runs aground in court, there could be others. In fact, one of the parties best positioned to sue Trump might be the D.C. government — if D.C. officials decided it was worth the risk to sue the president.

Below are four questions about the Emoluments Clause and what it might mean for President Trump.

1. What, exactly, is the Emoluments Clause?

It is 49 words in Article I of the Constitution.

“No Title of Nobility shall be granted by the United States: And no Person holding any Office of Profit or Trust under them, shall, without the Consent of the Congress, accept of any present, Emolument, Office, or Title, of any kind whatever, from any King, Prince, or foreign State.”

In this instance, the words that matter most are the ones we have placed in italics.

According to legal scholars, these words were added out of a concern from the 1700s that American ambassadors, on the far side of the ocean, might be corrupted by gifts from rich European powers.

Benjamin Franklin, for instance, had accepted a snuffbox festooned with 408 diamonds from the King of France. John Jay accepted a horse from the King of Spain.

After that, the Emoluments Clause rarely came up again. It’s never been the subject of a major court case and never been taken up by the Supreme Court, leaving great uncertainty about what it means — and to whom, exactly, it applies — in the 21st century.

2. Is President Trump violating the Emoluments Clause?

That’s uncertain.

The group that filed Monday’s lawsuit — whose attorneys include prominent ethics lawyers from the Barack Obama and George W. Bush White Houses — says Trump is in violation.

Their logic is that the clause prohibits Trump from taking any money at all from a foreign state. To them, the clause prohibits not just straight-up gifts but also payments for services rendered. So it would prohibit a Trump-owned hotel from renting a ballroom to a foreign embassy and prohibit Trump Tower from renting out office space — as it already does — to a state-controlled Chinese bank.

In their complaint, they ask a federal judge to stop Trump’s businesses from taking those payments.

“A federal officeholder who receives something of value from a foreign power can be imperceptibly induced to compromise what the Constitution insists be his or her exclusive loyalty: the best interest of the United States of America,” the group wrote in its legal filing.

Trump and his attorneys have rejected that idea.

Although Trump has promised to relinquish management of his companies to his two oldest sons and top executives, he will continue to own the businesses.

His attorney said Trump will avoid running afoul of the Constitution because his businesses will not be accepting gifts from foreign countries, rather they’ll be accepting payments, for services rendered.

“Paying for a hotel room is not a gift or a present,” attorney Sheri Dillon said at a news conference before his inauguration.

Dillon also sought to address a secondary concern — that foreign governments might turn those payments into gifts, by wildly overpaying Trump for a ballroom or a round of golf.

Dillon said that Trump would turn over “profits” from foreign governments at his hotels to the U.S. treasury. It is unclear, however, exactly how Trump’s businesses would calculate that, because the Trump Organization hasn’t provided any details on how such payments would be tracked, collected and dispersed.

Is that enough?

[For foreign diplomats, Trump hotel is place to be]

“Too many people are asserting more than they could possible know,” said Seth Barrett Tillman, a lecturer on American law at Maynooth University in Ireland who has studied the Emoluments Clause. “Until the courts speak — particularly the Supreme Court — we don’t know.”

3.) Will the lawsuit work?

That depends on what you mean by “work.”

Several legal experts have said they doubt a federal judge would give the watchdog group a full victory. One big question: Does the watchdog group even have “standing” to sue Trump in the first place?

“Just complaining about bad government does not give rise to standing — or you or I would have standing to challenge just about anything that goes on.” said Erik Jensen, a law professor at Case Western Reserve University in Cleveland. “And the system just couldn’t work.”

To have standing to sue, the watchdog group must show evidence it was harmed by Trump’s actions. The group says it can. The logic: Its workload has increased because Trump has given them new concerns to investigate.

“The injury to the organization is that it’s much more difficult to accomplish the organization’s mission,” said Richard Painter, a University of Minnesota law professor and former chief White House ethics lawyer for President Bush. He is one of the attorneys on the case and vice chairman of the watchdog group’s board. “Basically the administration has opened up a whole new avenue of corruption.”

Other legal scholars are skeptical about this. They say that nobody — especially not Trump — forced the watchdogs to work on this issue.

“This injury is self-inflicted,” Josh Blackman, a professor at the South Texas College of Law in Houston, wrote on his blog Monday. Therefore, he said, the argument “does not find support in the [Supreme Court’s] caselaw.”

It’s possible, however, that the lawsuit still could be a success for the watchdog group, even if a judge eventually rules against it.

If the case progresses far enough, for instance, Trump’s businesses might be forced to turn over documents that detail their dealings with foreign governments. Trump might be forced to turn over his tax returns, which he has refused to do. The watchdog group could then use those to unearth more details about Trump’s potential conflicts of interest — learning more about who he does business with and whom he owes money to.

[Trump won’t release his tax returns, adviser says, because people don’t care]

4.) Would somebody else have a stronger case?

Among those best positioned to raise the issue legally, according to experts, are business competitors who can demonstrate that they’ve lost clients or profits to Trump firms, particularly in cases where Trump’s presidency benefits his company.

Top on the list are hotels competing for that same foreign business, a group that includes investors from China, the United Arab Emirates and Qatar, as well as Washington-area developers and the D.C. government.

The owners of competing luxury hotels in the District include a range of large institutional investors, many of them from abroad. The Four Seasons in Georgetown, which lost thousands of dollars in business when the Kuwaiti Embassy decided to hold its National Day celebration next month at Trump’s D.C. hotel, is majority-owned by Anbang Insurance Group, a Chinese insurance giant affiliated with the Chinese government.

The Four Seasons hosted the Kuwaiti event in previous years and initially planned to hold the 2017 event there as well. Although event organizers said they were under no political pressure to hold the celebration at Trump’s hotel, that could place Anbang or another investor in the property, Chicago-based Strategic Hotels & Resorts, in position to take legal action.

Four Seasons Georgetown spokeswoman Liliana Baldassari is among those who has familiarized herself with the Emoluments Clause in recent weeks.

“We’ve been taking a look at it,” she said. She declined to comment however on whether the hotel’s owners would utilize it.

Other hotel owners may have similar standing to raise the issue. The W Hotel nearby, also popular with the embassy crowd, is majority-owned by the UAE government, through a subsidiary of the Investment Corporation Of Dubai, a sovereign wealth fund. The St. Regis Washington is owned by a subsidiary of a Qatari investment firm, Al Faisal Holding, that was founded and is controlled by the country’s richest man, Sheikh Faisal Bin Qassim Al Thani.

Suing the president, particularly one who freely uses Twitter to attack businesses and executives, would be a daunting effort for any business owner. For that reason, some experts expect attacks on Trump’s business to originate with Democratic leaders or officials rather than competitors.

In that case, there may be no Democrats better positioned to take aim at Trump over the Constitution than the District of Columbia’s mayor, Muriel E. Bowser (D), or its attorney general, Karl A. Racine.

Bowser and Racine may be loath to incite the new president, given the outsize influence the federal government has on the District’s laws and budget rules. Bowser met with Trump at Trump Tower in New York after the election, and she said the president-elect told her that “he is a supporter of the District of Columbia, he’s familiar with the District of Columbia, and he wants to be supportive.”

[Trump is a D.C. ‘supporter,’ mayor says after meeting with president-elect]

But Bowser and Racine have a particular entree should they choose to pursue it: The D.C. government owns the land beneath the Marriott Marquis hotel and lent $383 million in taxpayer funds to the project.

The District also owns the land under the Conrad Hotel, a luxury 360-room property that is under construction downtown and will compete directly with the Trump hotel when it opens in the first quarter of 2019.

“If D.C. can allege that it has lost economically because of the benefits derived from the Trump violation of that Emoluments Clause, then D.C. could sue,” argued Erwin Chemerinsky, dean of the University of California at Irvine School of Law and an American Constitution Society board member . “And the way to do that would be to show that foreign governments are sending business to the Trump hotel that would otherwise go to D.C.’s hotels.”

Bowser’s chief of staff, John Falcicchio, declined to comment, citing legal advice. Racine is already engaged in litigation with Trump because the president has sued the District over his hotel’s tax bill.

Racine’s spokesman, Robert Marus, issued a statement saying that “generally speaking, we at the Office of the Attorney General will consider any viable legal claim that would advance the public interest of the District of Columbia. However, it would be inappropriate at this point to speculate on any litigation strategy or potential cause of action in a specific case, including any Emoluments Clause claim.”