The government office overseeing ethics policy for the executive branch has turned down a request from a Democratic senator to investigate whether President Donald Trump’s business dealings violate a provision in the Constitution that limits the president’s compensation to his official salary.

In a letter Monday, U.S. Office of Government Ethics Director Walter Shaub told Sen. Patty Murray (D-Wash.) that his office lacks jurisdiction to examine whether benefits Trump gets from federal government dealings with his private businesses run afoul of the domestic emoluments clause in the Constitution.

"The emoluments issues are presently under judicial review, and, within the executive branch, are under the sole purview of the Department of Justice," Shaub wrote. "OGE has no authority to investigate or order corrective action on the part of the President. Ultimately, under the Constitution, the authority to oversee the Presidency rests with Congress."

Shaub, who was appointed by President Barack Obama to a five-year term that runs through early next year, has been outspoken in his criticism of Trump. The OGE director publicly denounced Trump’s plan to retreat from his businesses while he serves in the White House. Shaub also demanded ethics waivers the White House had not made public and he rebuffed a proposal from Trump’s lawyer to submit an unsigned financial disclosure form.

However, Shaub previously indicated to other members of Congress that his office has no authority to investigate Trump over conflict of interest issues or questions of whether he is violating the Constitution’s foreign emoluments clause. That provision prohibits U.S. officials from accepting payments from foreign governments. The earlier letters don’t appear to have directly addressed the more obscure domestic emoluments clause.

Murray’s office did not immediately respond to a request for comment.