Mary Ellen Callahan is a nationally recognized privacy attorney, with an extensive background in consumer protection law.  As the longest-serving former Chief Privacy Officer of the United States Department of Homeland Security – the first statutorily mandated privacy office in any federal agency – Ms. Callahan has a unique and broad knowledge of and experience with the interface of the protection of privacy, civil rights and civil liberties with cybersecurity and national security issues.  During her tenure at the Department of Homeland Security, Ms. Callahan also served as Chief Freedom of Information Act (FOIA) Officer, responsible for centralizing both FOIA and Privacy Act operations to provide policy and programmatic oversight and support implementation across the Department.  Ms. Callahan is the founder and Chair of Jenner & Block’s Privacy and Information Governance Practice.

Ms. Callahan has been recognized by Chambers USA with a “Band One” Nationwide ranking, Chambers’ highest ranking, in privacy and data security and by Legal 500 as a “Leading Lawyer” in technology: data protection and privacy.  In 2011, she received the select Federal 100 Award, which recognizes individuals in government and industry who have played pivotal roles in the federal government information systems community.  Ms. Callahan’s work on integrating cybersecurity, transparency and privacy at the Department of Homeland Security was cited as the reason for her Federal 100 recognition.  She is a prolific writer and speaker on privacy issues, including having testified before Congressional Committees numerous times in her capacity as Department of Homeland Security Chief Privacy/Chief FOIA Officer.  Ms. Callahan has served as Vice-Chair of the American Bar Association's Privacy and Information Security Committee of the Antitrust Division; Co-chair of the Privacy Committee of the CIO Council, the principal interagency forum for improving agency practices related to the design, acquisition, development, modernization, use, sharing, and performance of Federal information resources; and Co-chair of the Privacy and Civil Liberties Subcommittee of the Information Sharing and Access Interagency Policy Committee. She serves the Firm as a member of the Diversity & Inclusion Committee and is Co-chair of the Firm's Women's Forum Steering Committee. 

Prior to joining the Department of Homeland Security in 2009, as a partner in the DC office of an international law firm, Ms. Callahan focused on privacy, security, data protection, consumer protection, e-commerce, antitrust and competition issues across a wide variety of industries including retail, technology, entertainment, financial services, health care, telecommunications and government contracts. She advised businesses, including multinational companies, on a variety of privacy and information governance issues, including privacy and security policies; performed audits of clients’ privacy and security policies as related to relevant state and federal legislation and created and implemented requisite compliance strategies and programs; and drafted website privacy policies and terms of use. Ms. Callahan is also experienced as a litigator and has represented clients before federal administrative agencies, in federal and state courts in the District of Columbia and in federal courts in Virginia and New York.

Prior to law school, Ms. Callahan worked at the Congressional Research Service of the Library of Congress as part of the Special Task Force on the Development of Parliamentary Institutions in Eastern Europe.