March 2018 revealed a former CIA agent said the subpoena indicates Mueller is treating Trump’s team like a “criminal enterprise.”
17 May 2017, Rod Rosenstein (who was then the “acting” Attorney General for the U.S. Department of Justice) appointed Robert Mueller to lead a Special Counsel to “Investigate Russian Interference with the 2016 Presidential Election and Related Matters.” Order No. 3915-2017 (the Order).
[https://www.justsecurity.org/wp-content/uploads/2018/04/4-2-18-Rosenstein-Memo-to-Mueller.pdf