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John Guernsey represents clients in complex commercial litigation and fiduciary litigation, with a strong focus on restrictive covenant and trade secret matters as well as trust and estate matters. John has also served as lead counsel on intellectual property litigation, products liability and complex torts, and employment litigation.

John focuses his practice in federal and state courts in Pennsylvania and New Jersey, but he has appeared in courts from the Virgin Islands to Texas in representation of clients.


J.D., Harvard Law School, Cambridge, Massachusetts
B.S., with distinction, United States Military Academy at West Point


Selected as a Leading Lawyer for General Commercial Litigation in Chambers USA, The Client’s Guide to America’s Leading Lawyers for Business (2010–2022)

Listed as Best Lawyers in America Philadelphia “Lawyer of the Year” for Litigation – Trusts and Estates (2017)

Named among The Best Lawyers in America® for Commercial Litigation (2010-2024), Litigation – Labor and Employment (2011-2024), Litigation – Trusts and Estates (2011-2024) by Best Lawyers

AV® Preeminent™ Peer Review Rated by Martindale-Hubbell

Listed in Pennsylvania Super Lawyers (2005–present)


American Bar Association

Montgomery County Bar Association

Philadelphia Bar Association

Fellow, American College of Trial Lawyers


State Bar Licenses

Pennsylvania, New Jersey

Court Admissions

U.S. District Ct., E.D. of Pennsylvania
U.S. District Ct., M.D. of Pennsylvania
U.S. District Ct., W.D. of Pennsylvania
U.S. District Ct., District of New Jersey
U.S. Court of Appeals, 3rd Circuit
U.S. Court of Appeals, Federal Circuit