Margaret Pfeiffer was a partner of Sullivan & Cromwell from 1982 to 2008, resident in the Washington, D.C. office. She became senior counsel in 2011. Ms. Pfeiffer’s practice includes the representation of U.S. and non-U.S. clients of the Firm in state and federal courts throughout the country.
Among the areas on which her practice focuses is patent litigation. Ms. Pfeiffer has represented both patentees and accused infringers in actions before the federal courts and the International Trade Commission (“ITC”). Recent matters include the successful representation of Philips Electronics N.V. in enforcing patents related to recordable compact discs, in both the ITC and New York federal court, and defending VeriFone, Inc. in an ITC investigation and related litigation in California federal court, in which VeriFone was accused of infringing patents relating to credit verification point-of-sale devices. Ms. Pfeiffer has been selected by her peers for inclusion in the Best Lawyers in America for Patent Litigation (2008-2022).
As part of her practice relating to advising and representing clients in regard to investigations by government agencies, Ms. Pfeiffer has long experience with civil and criminal enforcement of U. S. economic sanctions and dealing with the Department of Justice and the U.S. Securities and Exchange Commission (“SEC”) in regard to proceedings under the Foreign Corrupt Practices Act. She has also long advised and represented clients in matters involving restrictions on non-U.S. investment in the United States, including dealing with the Committee on Foreign Investment in the United States.
Ms. Pfeiffer is also experienced in antitrust litigation and in merger-related investigations and dealings with the Antitrust Division of the Department of Justice and the Federal Trade Commission (“FTC”), and provides antitrust advice to a range of clients, including Koninklijke Philips Electronics N.V. and Nippon Steel Corporation, on an ongoing basis.
Ms. Pfeiffer oversees the pro bono practice in the Washington, D.C. office.
Professional Activities and Community Involvement
- Board Member, National Law Center on Homelessness and Poverty
- Vice Chair, Shakespeare Theatre Lawyers Committee
