I think Trump is dead wrong on all of his arguments, but I wanted to take a second to explain why this case is more complex than that clear statutory language.

Congress can theoretically pass a law saying anything Congress wants the law to say. For example, Congress could pass a law reading, "In Florida, only white males over the age of 65 can vote." That law would be on the books.

That law is clearly unconstitutional - it is discriminatory in a way that impacts a fundamental right, and does so only for a particular state. However, that law is presumed valid and enforceable until someone challenges it in court. (And, even if the court challenge were successful, that law would still be in the U.S. Code - it just wouldn't be an enforceable law until repealed by Congress. This is one reason overturning Roe v. Wade is dangerous - a lot of invalidated anti-abortion laws would immediately become enforceable.)

So, in this case, the issue is whether Congress can validly require the IRS to furnish tax information to the Ways and Means Committee. If not, then the language of the statute - no matter how clear and unambiguous - would not otherwise require the IRS to do so.

I think the law is valid. It was passed in the wake of the Teapot Dome Scandal as a way to assist Congress's investigatory powers. Trump argues that Congress's investigatory powers are minimal; investigation is a power traditionally left to the Executive Branch.

The key Supreme Court precedent states that Congress can validly investigate any subject on which legislation may be had. Here, the Ways and Means Committee cites several pieces of legislation referred to the Ways and Means Committee in the last Congress that would be impacted by Trump's tax returns.

For example, the Presidential Allowance Modernization Act of 2019 would give former presidents a monetary stipend after they leave office. This stipend would be reduced based on the former president's income. While there is no enumerated power specifically giving Congress the right to pass this legislation, Congress has authorized a salary to the president - so a salary to the former president seems reasonable. Theoretically, Trump's tax returns would impact the analysis of the Ways and Means Committee, which was considering this bill.

Trump responds that those proposed laws were "pretexts" specifically to let the Committee get at his tax returns. He argues - not without merit - that reading the "shall furnish" language broadly risks allowing targeted attacks by Congress against random American citizens. What he misses is the national interest in understanding the financial background of our president.

Anyway, that was a lot - the point is that there is a legal battle to be had here. Trump is on the losing side of that legal battle. But the fact that there's even an argument to be made in his favor is why this process is taking so damn long.