Lawyers representing about 200 Democratic members of Congress urged a federal judge on Thursday to allow them to press ahead with a lawsuit seeking to block President Donald Trump from taking payments and other benefits from foreign governments doing business with his corporate empire.

Nearly a year after the suit was filed, Judge Emmet Sullivan of U.S. District Court for the District of Columbia held the first hearing in the case on Thursday.

For two hours, lawyers for the members of Congress and the Trump administration battled over a key issue in the case: whether individual lawmakers have standing to sue the president over his alleged violations of the Constitution’s ban on accepting so-called foreign emoluments without advance approval from Congress.

For the Democratic lawmakers involved, however, it may have been worth the wait. Sullivan sounded sympathetic to their arguments, although he repeatedly cautioned observers not to read too much into his questioning of the attorneys.

Early in the hearing, Sullivan, an appointee of President Bill Clinton, noted that the Constitution appears to indicate that federal office holders must get Congress’ permission before accepting foreign gifts or gratuities. “That’s crucial,” the judge said, as he read through the lawmakers’ arguments in legal papers.

Sullivan repeatedly questioned why more lawmakers had not joined the suit and whether it would be stronger if it had the official approval of the House, the Senate or both. However, the attorneys pressing the suit argued that even a single lawmaker would have standing to pursue the issue.

“The way Congress gives its consent is through the votes of individual members,” said Brianne Gorod, an attorney for the lawmakers. “It doesn’t matter how that vote comes out. It’s that vote that matters.”

Gorod insisted that Trump has the obligation to come to Congress and request permission to accept the payments and that without such a request, Congress is essentially powerless.

“There is simply nothing the Congress can do,” she said.

While Sullivan did not sound totally convinced that individual lawmakers have standing to sue the president, the judge repeatedly said he was concerned that if members of Congress can’t raise the issue in court, it may be that no one can. At one point, he called that notion “troubling.”

In what could be an inauspicious note for Trump’s side, Sullivan greeted Justice Department attorney Brett Shumate by saying it appeared the government “overreached” in some of its written arguments that court precedents foreclose individual members of Congress from suing in a case like this one. “It seems like a stretch there,” the judge said.

Shumate insisted that lawmakers who want to come into court and press claims about Congress’ being bypassed need some official authorization. “Those institutional injuries can’t be asserted by individual members of Congress,” he said.

The government lawyer’s argument was a challenging one, however, because he was unwilling to concede that either house of Congress or any private parties would have standing to bring a suit. Such a concession, of course, would undercut the government’s position in other suits, including a couple that are pending.

Shumate noted that at least two measures are pending to try to rein in or disapprove Trump’s receipt of emoluments. “There’s no reason members couldn’t vote today on that resolution,” he said.

“That’s not going to happen, though,” the judge replied, noting that Republicans appeared unwilling to let those measures come to a vote.

“That’s not going to happen because these members have been unable to convince their colleagues to bring it up for a vote,” Shumate said.

Sullivan said he understood the “frustration” that lawmakers were not able to “do the job that the voters sent them to Congress to do.”

But Shumate insisted: “That’s the frustration of the political process.”

In the end, the legal issue appeared to turn on the consequences of congressional inaction.

Lawyers for the lawmakers insisted that without explicit advance approval from Congress, Trump was violating the Constitution by accepting foreign payments. The Justice Department attorney suggested that if there was any violation, Congress was free to use its powers to protest the president’s moves, but that the courts were the wrong venue to resolve such disputes.

The scene for the unusual lawsuit was one befitting a momentous case. The hearing took place before a near-capacity crowd in the federal courthouse’s capacious ceremonial courtroom, typically reserved for en banc circuit court arguments, naturalization ceremonies and investitures of new judges.

Two lead plaintiffs in the case, Sen. Richard Blumenthal of Connecticut and Rep. Jerrold Nadler of New York, sat at the plaintiffs table alongside their attorneys from a liberal public interest law group, the Constitutional Accountability Center. Rep. Sheila Jackson Lee of Texas was also on hand as the hearing began.

At a news conference outside the courthouse after the arguments, Blumenthal said the lawmakers’ suit was particularly crucial because senators and House members were the only obvious ones with a stake in blocking all the emoluments Trump may be receiving around the world — a sum the senator said probably amounted to hundreds of millions of dollars.

“We are the only game in town. We are the only ones who can enforce that right,” he said. “I was tremendously encouraged by today’s arguments.”

Asked why Congress couldn’t hold up the president’s appointments or cut off government funding, Blumenthal said such actions wouldn’t really address Trump’s private actions.

“Any of those supposed remedies would harm the American people, not the president,” the senator said. “There’s no adequate remedy that would not enact harm on the American people.”

Blumenthal and Nadler said Trump’s receipt of foreign payments presents national security concerns because the payments make it impossible to determine whether the president is offering concessions in security-related disputes with countries like China because of arm’s-length diplomatic negotiations or because of benefits his businesses receive from foreign governments.

Even if Sullivan concludes that the lawmakers have standing, other thorny legal issues await. Some legal experts contend that the foreign emoluments clause doesn’t even apply to the president. There are also questions of whether it reaches ordinary business transactions with foreign governments and how to decide whether a particular deal is actually a gift in disguise.

While the Democratic lawmakers’ suit has been pending, three other legal challenges over foreign payments to Trump’s businesses have seen action in other courts.

In December, a federal judge in New York tossed out a pair of suits targeting Trump’s practices on the issue, saying the cases raised “a non-justiciable political question.” One suit was brought by Citizens for Responsibility and Ethics in Washington (CREW), along with a group of employees and owners of hospitality businesses like restaurants and hotels. The other suit was brought by a local attorney as a class action on behalf of members of the general public. CREW is appealing the ruling.

Trump’s opponents did better in a Maryland federal court, where a suit brought by the state of Maryland jointly with the District of Columbia cleared a key hurdle in March. A judge said D.C. and Maryland had shown they could be suffering competitive harm if Trump’s hotel in Washington is diverting business from a D.C.-owned convention center and businesses in Maryland. Another hearing on that suit is set for Monday in Greenbelt, Maryland.