Marc Zwillinger

Marc Zwillinger

Founder & Managing Member

Office: Washington, DC

Phone: (202) 296-3585

Email me


Marc Zwillinger is the founder and managing member of ZwillGen PLLC. Marc counsels on issues related to the laws governing Internet practices, including issues related to the Electronic Communications Privacy Act (“ECPA”), the Foreign Intelligence Surveillance Act (“FISA”), data privacy, use of alternative data for investment evaluation and fantasy sports and Internet gambling. He also helps Internet Service Providers and other clients with their compliance obligations pertaining to the use and disclosure of customer and subscriber information.

Marc also works with clients who have suffered security breaches in managing the incident response, conducting internal investigations, complying with security breach notification laws, and responding to FTC and state Attorney General inquiries.

In 2008 Marc made history by representing Yahoo! in its litigation with the government over the government’s effort to force Yahoo! to comply with directives issued under the Protect America Act, the precursor to the FISA Amendments Act. In that case, he appeared before the Foreign Intelligence Surveillance Court of Review, and is believed to be the only private lawyer ever to do so. He appeared before the FISA Court of Review again in 2016 as an appointed amicus curie. He continues to work on national security and foreign intelligence matters and holds a Top Secret security clearance.

Over the past two years, Marc has represented Internet clients in seven FTC investigations involving data security, data privacy, and advertising practices. He has negotiated settlement agreements with the NY & MD state Attorney General offices, and defended media and Internet companies against privacy class actions brought under ECPA, CFAA, the VPPA, and the VRPA.

In both the Chambers USA and Chambers Global guides, Marc is listed as a leader in the field of Privacy and Data Security law. Prior to founding ZwillGen, Marc ran the Privacy and Security groups at Sonnenschein Nath and Rosenthal and Kirkland & Ellis. Before that, he spent three years prosecuting cybercrime from the Computer Crime and Intellectual Property Section of the Criminal Division of the Department of Justice.

Since 2004, Marc has briefed and argued appellate cases before the Court of Appeals for the 1st, 3rd, 5th 7th, 9th, and 11th Circuit Courts as well as the Foreign Intelligence Surveillance Courts.

After receiving his J.D. from Harvard Law School, magna cum laude in 1994, Marc clerked for Judge Mark L. Wolf of the United States District Court, District of Massachusetts.

Marc is frequently invited to testify before Congress, speak to various professional audiences, and conduct in-house training courses. He has appeared on national news programs including CNN’s The Situation Room, ABC’s World News Tonight, Good Morning America, and C-Span’s Washington Journal. He is also an adjunct professor of Cybercrime at the Georgetown University Law Center in Washington, D.C. and on the board of George Washington University Law School’s Privacy and Security Council.



Ranked in Chambers USA, Band 1 (2021)
View profile


Harvard Law, J.D., 1994, magna cum laude

Tufts University, B.A., 1991, magna cum laude


Sonnenschein Nath and Rosenthal, LLP, Chair of Privacy and Security Group

Kirkland & Ellis, LLP

Department of Justice, Computer Crime and Intellectual Property Section of the Criminal Division


United States Supreme Court

United States Court of Appeals for the 1st, 3rd, 4th, 5th, 7th, 9th, and 11th Circuits

United States District Court for the Northern District of Illinois

District of Columbia Court of Appeals

Illinois Supreme Court


District of Columbia