The Statute of Limitations does not run when fraud is involved,
Although Mueller is a fraud, where has he committed the legal definition of fraud?
My opinion is that he would never ever be convicted of fraud even if he commuted criminal fraud.
He would need to be charged with murder and found with a bloody knife in his hand or something similarly unspeakable and improbable in today’s insane political climate.
Sessions is actually doing president Trump a favor in leaving Mueller alone. The firestorm of nut cases that erupted over McCabe would look like nothing should he fire Mueller.