Marc Zwillinger

Marc Zwillinger

Founder & Managing Member

Office: Washington, DC

Phone: (202) 296-3585

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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, deployment of AI, 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.

Marc has represented clients in more than a dozen FTC and state AG investigations involving data security, data privacy, and advertising practices, many of which have been closed with no action taken against clients. He has also negotiated settlement agreements, consent decrees, and assurances of discontinuance with the FTC and with Attorneys General office’s in New York, Massachusetts, and Maryland.

He also regularly litigates class actions involving data privacy, including several major victories on motions to dismiss in SCA and VPPA claims. For example, in 2023-2024 he successfully negotiated two class-action settlements under the VPPA, along with numerous individual settlements.

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. Since then, he has argued several classified matters in the FISC and FISCR, both in contested cases and as an amicus curiae. He continues to work on national security and foreign intelligence matters and holds a Top Secret security clearance.

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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Recognized by Lawdragon as a Leading Global Cyber Lawyer
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Harvard Law, J.D., 1994, magna cum laude

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

MIT Sloan and MIT CSAIL Executive Education Course – Artificial Intelligence: Implications for Business Strategy


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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