The House Ways and Means Committee has subpoenaed the Treasury Secretary and IRS Commissioner for six years of President Donald Trump’s tax returns after to Department of Treasury Secretary Steven Mnuchin ignored Democrats’ request.

The subpoenas, requesting the president’s returns by May 17, follow Democrats’ request for the information under an obscure 1920’s-era provision of the tax code requiring that the Treasury Secretary “shall furnish” requested tax information to Congress.

The president’s lawyers and White House are expected to challenge the move and have argued that Democrats’ request does not serve a legislative purpose, an argument the administration made in its rejection of Democrats’ initial request.

House Ways and Means Chairman Richard Neal said in a statement that the request was made to determine whether IRS audits and enforcement of the federal tax code of sitting presidents need to be codified into law.