Mary Marks Lathom

Mary Marks Lathom is a Senior Attorney at Cassidy Law PLLC who advises businesses on government contracting, ethics and compliance, internal investigations, international trade, and national security matters. Her work includes government audits and investigations, government contracting compliance, ITAR and export controls, CFIUS, NISPOM requirements, cybersecurity, independent monitorships, and mediation. She focuses on practical strategies that connect legal compliance with operational and business objectives.

Mary earned a BA in English from Penn State University, studied law at Duquesne University’s Kline School of Law, and received an MPP from the University of Chicago. She is admitted to practice in Washington, D.C., Illinois, and Pennsylvania. Her multidisciplinary education supports her ability to evaluate regulatory requirements, policy considerations, and business risks while helping organizations develop workable approaches to complex compliance and government-facing matters.

Mary has served in senior in-house and government roles as well as private practice. Before joining Cassidy Law, she led enterprise ethics, trade, and compliance programs at MasterBrand and Coherent Corp. She previously practiced international trade law in Washington, D.C., and served as Assistant General Counsel and Attorney-Advisor at the FBI. That background informs her work on investigations, federal contracting, export controls, foreign ownership concerns, and operational compliance.

Mary Marks Lathom also contributes to professional education on compliance and cybersecurity issues, including presentations for the D.C. Bar and the Public Contracting Institute. She completed 40-Hour Basic Mediation Training through The Conflict Lab in 2025 and works as a certified mediator. Her experience across private practice, government, and in-house leadership supports clear, cost-conscious advice for organizations managing legal risk, government requirements, and cross-border business concerns.

Law Office Affiliations

• Attorney, Cassidy Law PLLC
• Member, District of Columbia Bar
• Member, Illinois State Bar Association
• Member, Pennsylvania Bar Association

Licensed State

• District of Columbia
• Illinois
• Pennsylvania

Education

• University of Chicago
  Master of Public Policy (MPP)
• Penn State University
  Bachelor of Arts (BA) in English

Awards & Badges