an attorney general from exercising the powers conferred on the attorney general by the laws of such State to conduct investigations or to administer oaths or affirmations or to compel the attendance of witnesses or the production of documentary and other evidence. (c) Venue Any civil action brought under subsection (a) in a district court of the United States may be brought in the district in which the defendant is found, is an inhabitant, or transacts business, or wherever venue is proper under section 1391 of title 28, United States Code. Process in such action may be served in any district in which the defendant is an inhabitant or in which the defendant may be found. (d) No preemption Nothing contained in this section shall prohibit an authorized State official from proceeding in State court on the basis of an alleged violation of any civil or criminal statute of such State.