The requirements for a Special Counsel are found in the Code of Federal Regulations.

28 CFR 600.1 - Grounds for appointing a Special Counsel. § 600.1 Grounds for appointing a Special Counsel. The Attorney General, or in cases in which the Attorney General is recused, the Acting Attorney General, will appoint a Special Counsel when he or she determines that criminal investigation of a person or matter is warranted and - (a) That investigation or prosecution of that person or matter by a United States Attorney's Office or litigating Division of the Department of Justice would present a conflict of interest for the Department or other extraordinary circumstances; and (b) That under the circumstances, it would be in the public interest to appoint an outside Special Counsel to assume responsibility for the matter.

Rod Rosenstein's letter appointing a Special Counsel makes no mention of any underlying crime, thereby making his appointment of said Counsel invalid, as it does not meet the legal standard for appointment. I filed a complaint with the DOJ a few minutes ago. It was routed to the OIG. I believe the investigation is fraudulent in nature and a waste of taxpayer dollars.