I understand as a “Special Council” he can investigate anything he wishes. Such as the Clinton corruption and collusion with Russia. The Obama Justice Department obstruction of justice regarding Hillary etc.
Another option is to nominate ANOTHER Special Counsel, like Rudy Giuliani.
What the DOJ can do at any time is redefine scope and duties.
Nominate Rudy to handle everything the good guys want and limit Mueller to a couple of items which have already been debunked and tied to people he has personal relationships with, forcing him to recuse/resign.
Done and done.
Mueller has a narrow charter, which is to take up and close out a certain set of investigations that were open in the FBI. He can open new lines of inquiry to the extent that there is obstruction of those few investigations.
The Lynch/Comey obstruction is not part of his charter, nor is the Hillary private server, and likely a hundred or more other crimes committed by the DEMs in the course of the 2016 election.
I don't have a problem if Mueller comes out of his own volition, and closes the investigation on the basis of Comey's testimony yesterday. I don;pt think that fits his pattern of being thorough.
We'll learn much about Mueller's political chops (he's not supposed to be political in this job, but maybe he is) by the content of his report.
I don't think the question of Trump obstructing justice is part of Mueller's charter. That investigation could NOT be open at the time Mueller got his assignment. If he sweeps it in, and treats it using the Dersh model (presidents, with pardon power, can't obstruct justice by closing an investigation), he's not being a political animal. If he hems and haws that the president has no authority to step on the FBI independence, he's a committed part of the swamp.