The battle for President Trump’s personal finances was never going to be an easy one, and lawyer William Consovoy has now ramped it up. Following House Democrats’ formal request for Trump’s individual and business tax returns from 2013 through 2018, Trump’s personal attorney sent a letter to the U.S. Treasury on Friday arguing their release would serve no “legitimate legislative purpose.”

“Even if Ways and Means had a legitimate committee purpose for requesting the president’s tax returns and return information, that purpose is not driving Chairman [Richard E. Neal]’s request,” said Consovoy in his letter. “His request is a transparent effort by one political party to harass an official from the other party because they dislike his politics and speech.”

According to The New York Times, Consovoy’s request invoked the somewhat-obscure Section 6103 of federal tax code, allowing tax-writing committees to “confidentially measure how changes to the tax code would affect different types of taxpayers”—in this case the president. Ways and Means’ request gave the I.R.S. until April 10 to provide the returns, though the House may end up in a years-long legal challenge if the I.R.S. refuses to comply. Ways and Means could potentially issue a subpoena, which may reach all the way to the Supreme Court.

Granted, Consovoy’s letter on the matter holds no actual authority, and neither the I.R.S. nor Treasury Department have responded publicly to the request. Neal is said to have worked with House lawyers to shore up its legal standing, claiming access to Trump’s returns will help measure “the extent to which the I.R.S. audits and enforces the federal tax laws against a president.”

Asked on Friday about the effort to keep his financial information private, Trump retreated to his familiar claim that he’s under audit. “Oh, I don’t know,” he told reporters upon leaving the White House for his visit to the southern border. “That’s up to whoever handles it. I don’t know. Hey, I’m under audit. But that’s up to whoever it is. From what I understand, the law is 100 percent on my side.” It’s also been speculated that Trump pressed Mitch McConnell to expedite the confirmation of Michael Desmond to chief counsel of the Internal Revenue Service; potentially to protect himself from Democratic oversight.

Consovoy, meanwhile, has pressed that Trump’s rights as a private citizen supersede scrutiny of a president’s financial history. “If Chairman Neal genuinely wants to review how the I.R.S. audits presidents, why is he seeking tax returns and return information covering the four years before President Trump took office?” Consovoy asked. “Why is he not requesting information about the audits of previous presidents?”

Should the I.R.S. and Treasury opt to fulfill Neal’s request for six years of Trump’s tax returns, the Ways and Means committee would still have to vote to disclose any of its findings.