John has handled complex commercial, employment, regulatory, and appellate cases at all levels of the American legal system for more than four decades. He has conducted numerous jury and bench trials in both federal and state court and administrative hearings before a number of federal and state agencies. Mr. Simpson is experienced in the conduct of complex, protracted federal court litigation and has a deep background in federal administrative law involving multiple U.S. regulatory programs. Mr. Simpson also has several decades of experience in employment law and has handled discrimination claims in federal and state court, with several precedent-setting cases. He has argued 19 appeals in various federal and state courts.Recently, Mr. Simpson achieved a national profile in the area of animal law and animal rights litigation. Mr. Simpson tried a landmark case under the Endangered Species Act to a defense verdict for the client in a case that received international media attention and in which the court made an explicit finding that Mr. Simpson had "pulverized" the testimony of the plaintiff and lead witness on cross examination. [677 F. Supp.2d 55, 67 (D.D.C. 2009), aff'd, 659 F.3d 13 (D.C. Cir. 2011)]. In that same litigation, Mr. Simpson obtained an unprecedented ruling that the client was entitled to recover attorneys' fees because the court found the plaintiffs' case to be "frivolous," "vexatious," and "groundless and unreasonable from its inception." This ruling, the first in favor of a private defendant under the 47-year old Endangered Species Act, paved the way for the recovery by the client of more than $25 million from the adverse parties, which represented a 100 per cent recoupment of the legal fees expended on the case. This was reportedly the largest lodestar attorneys' fee claim ever made in the U.S. District Court for the District of Columbia and one of the largest fee recoveries ever under the Christiansburg Garment Co. v. EEOC standard.

Represented several NFL players in contract negotiations, injury grievances and other matters with NFL clubs.

John served in the Marine Corps as a rifle platoon leader, 81mm mortar platoon commander, company executive officer and company commander with the Third Battalion, Fifth Marine Regiment, First Marine Division. He comes from a military family that has more than 100 collective years of active duty service in the Army, Navy, Air Force, Marines and Coast Guard.