WOW Apparently special counsel must already be Presidential appointed and Senate confirmed. Meaning, Rosenstein (technically Sessions) doesn't have the power to crown just anyone to special counsel...
"The short answer to this as a statutory basis for constitutionalizing Mueller’s appointment as a special counsel is that Mueller was not actually appointed to assist U.S. attorneys or to prosecute Indians. There is, therefore, no statutory authority for the Mueller appointment.
According to 28 U.S.C. 519, the attorney general has the power to "supervise all litigation to which the United States, an agency, or officer thereof is a party, and shall direct all United States attorneys, assistant United States attorneys, and special attorneys appointed under section 543.” But this reference creates no new inferior officers just as 28 U.S.C. 543 creates no new inferior officers. Both clauses refer to attorneys already appointed by law who are assisting U.S. attorneys, which is not what Robert Mueller is doing.
The Appointments Clause creates a default rule that all officers of the United States are principal officers who must be nominated by the president and confirmed by the Senate. It takes affirmative action by passing a statute for Congress to vest in the attorney general the power to appoint an inferior officer to be a special counsel. Since Congress has never passed such a statute, Robert Mueller is not, and cannot be, an inferior officer."
http://thehill.com/opinion/judiciary...pecial-counsel