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 where he counsels clients on issues related to the laws governing Internet practices, including issues related to ECPA and FISA, data privacy, information security, third-party data demands, content moderation, collection and use of alternative data, and fantasy sports and Internet gambling. Marc works on issues arising under state and federal data privacy, security breach, and surveillance statutes, such as ECPA, VPPA, CFAA, BIPA, and CCPA. He 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. Marc also helps Internet platforms work on content moderation and deplatforming issues, including the development of Ethical Use Frameworks.

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 (FISCR), and is believed to be the only private lawyer ever to do so. He appeared before FISCR again in 2016 as an appointedamicus curiae. He continues to work on national security and foreign intelligence matters and holds a Top Secret security clearance.

Marc has represented Internet clients in seven FTC investigations involving data security, data privacy, and advertising practices. He has negotiated settlement agreements with the New York and Maryland state Attorney General offices, and defended media and Internet companies against privacy class actions brought under ECPA, CFAA, VPPA, and 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 Circuits as well as the Foreign Intelligence Surveillance Courts, and he is one of a select group of amici curiae appointed to serve the Foreign Intelligence Surveillance Court.

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.



Ranked in Chambers USA, Band 1
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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



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