@edpc
If it isn't directly related to collusion then its outside of Muellers power. If the evidence was collected from another investigation its outside of his power.
An unlimited witch hunt isn't what this country is about.
That's where the redacted memo comes in. This judge believes he needs to see the memo, reviewed in private, to make a decision. They'll either let him see it, unredact some more, but not all, or decline.
The SC, under any administration, is not unfettered. They can only investigate what the AG (or acting) allows when it's presented to them. The AG directing the SC can say no to avenues of investigation or shut it down entirely. The president can also step in, if he choses. Yeah, it'll make waves and be very unpopular with some people, but they can't stop him. The SC is very fettered.
Trump won't fire Mueller, Rosenstein, or Sessions for a couple reasons. First, despite what we hear, he's not the confrontational fighter we've been told he is. That was apparent in the ways he handled the firings of Comey and Tillerson. Also, without those people, he cannot demagogue the issue. Once he fires them, he's the sole focus of criticism and responsibility.