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Marc De Leeuw


Marc De Leeuw

New York +1-212-558-4219+1-212-558-4219 +1-212-558-3588+1-212-558-3588
[email protected]
Marc De Leeuw has been a partner at Sullivan & Cromwell since 2001. His litigation practice includes representing clients in a variety of areas, including intellectual property, securities, antitrust, real estate, contract, bankruptcy, and many other commercial matters. 

Mr. De Leeuw has represented clients before arbitration tribunals, the International Trade Commission, New York and New Jersey state trial and appellate courts, numerous federal district courts and Courts of Appeals and the U.S. Supreme Court. He has participated in trials and arbitration hearings in intellectual property, antitrust, tort, contract and insurance cases. 

Professional Activities and Community Involvement
  • Serves as Chair of the Board of Directors of Mobilization for Justice
  • Represented pro bono the St. Andrew’s Society of the State of New York
  • Served on the New York City Bar Association Judiciary Committee 
  • PLI Panel Member, “Handling a Securities Case: From Investigation to Trial and Everything in Between” (2012, 2013)
  • Author of “Recent Patent Decisions and How They Affect Patent Law,” in Developing a Patent Strategy (2010) 
  • Speaker at professional conferences concerning investment company and patent litigation
  • Concurrences Review – Best Antitrust Business Article: Intellectual Property Category (2020)
  • New York Super Lawyers (2010, 2013, 2014, 2015, 2016, 2017, 2018, 2019, 2020)
  • AmLaw Litigation Daily – Runner-up, “Litigator of the Week” (December 2018, January 2019, October 2019)
  • The Legal 500 United States (2015)
  • Benchmark Litigation – Future Star (2020 – 2022)
  • National Law Journal – Bristol v. Microsoft named one of the “major civil-suit verdicts that beat the odds” (May 2000)


Intellectual Property
  • ​Representing Ocado in multiple cases against AutoStore relating to patents on robots and cubic auto storage and retrieval systems
  • Representing 15 major universities in a joint patent licensing program called University Technology Licensing Program (“UTLP”)
  • Representing AB InBev and Modelo in trademark infringement and contract actions involving sales of Patagonia beer and Corona Hard Seltzer
  • Representing Novo Nordisk in a variety of patent and false advertising matters, including in patent infringement actions, an ITC investigation involving patents on hemophilia drugs, an arbitration involving royalties on diabetes products, and a false advertising action involving advertisements for diabetes drugs
  • Representing Audio MPEG, Philips, TDF, and IRT in a patent infringement action against Dell involving patents on MP-3 technology
  • Representing Philips Electronics in patent infringement actions, including obtaining a substantial verdict at trial with an award of attorneys’ fees, and in successful appeal concerning infringement of Philips’ patents on universal remote control technology and in worldwide litigation involving Philips’ patents on cellular, CD, and DVD technology
  • Representing MobileMedia Ideas in patent infringement actions against Apple, RIM, and HTC involving multiple patents on smartphone technology
  • Representing General Electric, LG Electronics, Mitsubishi Electric, Samsung, BT, Thomson Licensing, Columbia University, Philips, JVC, and Sony in actions against Lenovo and Haier for infringing patents essential to the MPEG-2 and ATSC digital video compression and transmission standards 
  • Representing VeriFone in actions involving its patent on payment terminal security, false advertising claims, and contract and tort claims, including obtaining the denial of a preliminary injunction of VeriFone’s advertising of free service for competitors’ customers 
  • Representing Dyson in patent and false advertising litigation concerning the design of its vacuum cleaners and advertising claims, including obtaining summary judgment in two actions dismissing plaintiffs’ patent claims against Dyson
  • Representing Labatt in a patent infringement action, including at trial, involving its patent on a method for brewing “ice” beer
  • Representing Fonar, a manufacturer of MRI scanners, in a successful appeal to the U.S. Court of Appeals for the Second Circuit seeking to protect Fonar’s copyright on its maintenance software
  • Representing Abiomed and its CEO and CFO in securing dismissal of all claims in a putative securities class action filed in the Southern District of New York
  • ​Representing BP in multiple securities, shareholder derivative, and ERISA class actions arising out of the Gulf of Mexico and Prudhoe Bay oil spills, including in obtaining dismissal of the federal shareholder derivative action on the ground of forum non conveniens and dismissal of a class action challenging the cancellation of a BP quarterly dividend
  • Representing Ally Financial (formerly GMAC) in a securities class action based on disclosures about Ally’s subprime auto loan business, including obtaining dismissal of the action in Michigan state court for failure to plead an actionable false or misleading statement
  • Representing Banco Bradesco in a securities class action relating to Brazil’s “Operation Zelotes” tax corruption investigation
  • Representing various mutual funds and their directors in investigations and civil actions concerning board decisions and fund practices 
  • Representing Barclays in nationwide Enron litigation, including a securities class action and related proceedings and obtaining reversal of the district court’s decision to certify a class of Enron shareholders to pursue securities claims against Barclays and others seeking $40 billion in damages
  • Representing Cablevision in shareholder derivative and class actions concerning options “backdating” and “going private” offers
  • Representing Ally Financial in multiple antitrust class actions relating to trading of GameStop and other stocks in so-called “short squeeze” purchases
  • Representing Novo Nordisk in an antitrust class action alleging Novo sought to exclude generic competition for its Prandin® diabetes drug 
  • Representing Microsoft in a variety of private antitrust and related matters, including at a preliminary injunction hearing and seven-week trial in successfully defending against an antitrust action brought by Bristol Technology; in an antitrust and copyright action brought by Sun Microsystems, including through a preliminary injunction hearing and appeal; and in an antitrust action brought by Netscape Communications
  • Representing Fonar at trial in a successful defense of antitrust claims alleging monopolization of an alleged market for service of Fonar MRI scanners
Other Commercial Matters
  • Representing Barclays in a suit brought by a hedge fund arising out of termination of a $1 billion total return swap transaction, including a complete trial victory after which the New York Supreme Court held that Barclays had no liability to the hedge fund, and the appeal, in which the Appellate Division, First Department, unanimously affirmed that trial victory
  • Representing the New York Football Giants and New York Jets in litigation against the New Jersey Sports & Exposition Authority and developers of the proposed “American Dream” mall in New Jersey seeking to prevent construction of that mall
  • Representing Eisai in a breach of contract action against Pfizer and Viatris relating to sales of the generic form of Lyrica® in Japan
  • Representing Vornado Realty Trust in actions brought by Donald Trump relating to the sale of the “Riverside South” properties on the West Side of Manhattan that Trump claimed undervalued the properties by more than $1 billion, and in actions relating to properties including those at the Georgetown Park Mall, Times Square, Union Square South, and Harlem Park
  • Representing Canary Wharf in pursuing a $780 million claim in the Lehman bankruptcy
  • Representing J.C. Flowers & Co. in a breach-of-contract action brought by investment funds after Flowers terminated a stock purchase agreement for the sale of a controlling interest in an insurance company, including obtaining, on appeal to the Appellate Division of the New York State Supreme Court, First Division, reversal of plaintiffs’ $17 million summary judgment award and dismissal of the complaint in its entirety
  • Representing Oxford Health Plans (now part of UnitedHealth Group) in a variety of matters related to health insurance and reinsurance, including in arbitrations over rescission claims made by reinsurers and in a variety of private and class actions and “class arbitrations” brought by physicians and medical societies concerning Oxford’s reimbursement policies and practices
  • Representing The Bank of New York in investigations and civil actions concerning the Bank’s business with certain Russian customers
  • Representing Softbank in connection with contract, tort and fiduciary duty claims brought by a video game development company in which Softbank invested