The law is clear and the oversight position of Congress and this law is established already. Their bounds have been long established but Trump doesn't care about himself being the President without bounds. BTW, Congress does not have to "create law" to do this as "legislative intent" is a red herring. As a result of any hearing or oversight function there is the potential that legislation may occur but that it does isn't required. No legislation needs to be on the table and again courts get it.
As Mnuchin doesn't understand what yes or no mean or understand "did you ask the IRS to not comply", there is demonstrated ill intent to comply with law that has been determined to be lawful and Constitutional in the past, so arrest him on contempt and the system will function exactly as it should, well better at least.
So far no one has even attempted to explain a coherent legal or governance theory where Congress is authorized by the Constitution to remove the president if he is committing crimes but is barred by the Constitution from compiling evidence as to if he is committing crimes.
