Fox News senior judicial analyst Judge Andrew Napolitano said President Trump being under audit is not a defense against House Democrats' request for his tax returns.

In a letter to IRS Commissioner Charles Rettig, House Ways and Means Committee Chairman Rep. Richard Neal (D-Mass.) formally requested the IRS provide six years of Trump's personal and business tax returns.

Speaking to reporters Wednesday, Trump dismissed the request, saying, "Is that all? Usually it's 10. So I guess they're giving up. We're under audit, despite what people said, and we're working that out -- I'm always under audit, it seems, but I've been under audit for many years, because the numbers are big, and I guess when you have a name, you're audited. But until such time as I'm not under audit, I would not be inclined to do that."

On "Fox & Friends" Wednesday, Napolitano revealed he wasn't aware of this "obscure statute" in federal tax code until Neal cited it in his letter to Rettig.

"But it’s a law of the land, a federal statute that says the chair of the House Ways and Means Committee and/or -- meaning they don't have to act together -- the chair of the Senate Finance Committee can ask for anybody's tax returns. And the secretary -- meaning the secretary of the treasury, for whom the IRS works -- shall furnish them. They don't have to give a reason."

He said the "rub" is that those tax returns must be kept secret and confidential, but he explained how Democratic lawmakers can circumvent that rule.

“If these tax returns go to the House Ways and Means Committee and any member of Congress gets them, that member of Congress can go to the floor of the House of Representatives and the tax returns of the president of the United States become public," Napolitano said, warning that if they can do this to the commander-in-chief, "they can do it to anybody."

He said that he doesn't see what argument Treasury Secretary Steve Mnuchin could make against complying with Democrats' request and turning over the tax returns.

"I understand the president's argument that he's under audit. An audit is private, so if he's under audit, he knows, the people doing the audit know it, the public doesn't know it. That would not be a defense,” Napolitano said. “I’m sure this is going to end up in the court, because Mnuchin is not going to release it voluntarily, even though the statute says he must."

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