Regarding Trump's tax returns, "shall furnish" is mandatory language—no exceptions. For those who say, "What if the duly appointed Congressional committee chair sought his ex-wife's returns?" the answer is THE IRS WOULD STILL FURNISH THEM but the EX-WIFE would seek an injunction.
1/ And that's *exactly the point of the statute*. Congress wanted to make sure that *no one anywhere in the executive branch* could refuse Congress's request. It could not and did not stop private citizens from seeking injunctions. The GOP has no legal leg to stand on whatsoever.
2/ And incidentally, under the rules of statutory interpretation, it's likely that the only basis for an injunction would be a showing that the Congressman in question had a criminal or otherwise illegal purpose for seeking the return. But that's *not Mnuchin's argument to make*.
You can follow @SethAbramson.