Which brings us to the main point: England’s King George III was above the law, but the founders of our republic wanted a system that would divide power and have the branches check one another. The idea that only the president can investigate the president is an argument for autocrats, not Americans.
Trump says “trust me,” but that was exactly the argument the founders rebelled against. They knew that public officials would not always be angels, and that power had to be checked and dispersed. As James Madison put it in Federalist No. 51, “It may be a reflection on human nature, that such devices should be necessary to control the abuses of government.”
The only redeeming quality of Trump’s legal brief is its seeming, grudging acknowledgment that Congress’s powers might be greater in an impeachment proceeding. That has things only half-right. Yes, Congress could investigate Trump’s finances in an impeachment proceeding, but it can do so without launching the formal process of impeachment.
That said, Trump’s brief can be construed as an invitation to commence impeachment proceedings.