On Friday, Treasury Secretary Steven Mnuchin refused to comply with a subpoena from House Democrats to release President Donald Trump‘s tax returns.

The subpoena by House Ways & Means Committee Chairman Richard Neal asked for six years of Trump’s tax returns. The subpoena is backed by a 1924 federal law that says the treasury department should hand over any tax returns that are requested by the chairs of congressional tax writing committees.

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Neal predicted the request being denied earlier on Friday stating, “We will likely proceed to court as quickly as next week.”

“We are unable to provide the requested information in response to the Committee’s subpoena,” wrote Mnuchin in an open letter. Mnuchin said he consulted with the Justice Department and stated he would not comply with the subpoena because it “lacks a legitimate legislative purpose.”

“The law, by its terms, does not allow for discretion as to whether to comply with a request for tax returns and return information,” responded Neal in a written statement, following the Treasury Secretaries decision.

The requests by Neal for six years of the president’s tax returns started in early April as part of Congress’s duty to conduct oversight of government officials. The requests were necessary according to Neal because “the IRS has a policy of auditing the tax returns of all sitting presidents and vice-presidents, yet little is known about the effectiveness of this program.” Neal has stated that “On behalf of the American people, the Ways and Means Committee must determine if that policy is being followed, and, if so, whether these audits are conducted fully and appropriately.”

Trump is the first president to not release his tax returns since the end of Richard Nixon’s presidency in 1974.