A federal judge on Friday gave the go-ahead to a lawsuit led by Sen. Richard Blumenthal and joined by dozens of congressional Democrats who claim President Donald Trump has violated the U.S. Constitution by failing to seek and obtain the consent of Congress before accepting benefits from foreign states.

Blumenthal v. Trump is based on the Constitution’s emoluments clause, which bars presidents from taking payments from foreign states.

It says Trump violated the clause because his businesses, including his hotel in downtown Washington D.C., has hosted foreign embassy events and visiting foreign officials.

Blumenthal said he is “extremely gratified” by the court’s decision.

“No president is above the law,” he said.

Blumenthal says the president is violating the emoluments clause by his ownership of Trump Tower, which has foreign states among its tenants, and by the Chinese government’s granting of 40 trademarks to the Trump Organization.

The lawsuit gives several examples of former presidents who obeyed the rules of the clause, including Martin Van Buren, who in 1840 was offered two horses, a case of rose oil, five bottles of rose water, a package of cashmere shawls, a Persian rug, a box of pearls, and a sword by the Imam of Muscat.

The suit said that that Van Buren, writing to the Imam, explained that “a fundamental law of the Republic which forbids its servants from accepting presents from foreign States or Princes, precludes me from receiving” the items and that Van Buren then told Congress about the gifts.

The White House had argued that Congress could address the issue by passing legislation that prohibited the president from taking foreign gifts.

But the court disagreed.

In his ruling, Judge Emmet G. Sullivan wrote that the members of Congress “appropriately seek relief in federal court” because they have no way to address their concern about Trump’s alleged violation of the emoluments clause with legislation.

The court, however, has not ruled on the White House’s motion to dismiss the suit because it argues the benefits Trump has received are not emoluments.

“The next step will be to overcome their legal objection to what constitutes an emolument,” Blumenthal said. “But I think we will move forward.”

If the lawsuit advances, the plaintiffs can ask Trump and his businesses to turn over a number of financial documents, including the president’s tax returns, which he has declined to release.

“It’s not the goal of the lawsuit to make the tax returns available,” Blumenthal said. “But they would be relevant to the case.”

The Founding Fathers, especially Alexander Hamilton, were concerned about foreign corruption in the United States and wrote the Foreign Emoluments Clause into the Constitution. It requires the nation’s presidents to clear any gift or payment from a foreign leader with Congress.

About 200 congressional Democrats joined Blumenthal in the lawsuit, including several from Connecticut. The lawsuit was filed by the Constitutional Accountability Center, a liberal think tank.