image description

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.

Marc 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 represented clients in trials and arbitration hearings in intellectual property, antitrust, tort, contract, and insurance cases.

Marc has been recognized many times as a New York Super Lawyer and as a “Future Star” by Benchmark Litigation.  He has been named multiple times in the AmLaw “Litigator of the Week,” and by the National Law Journal for his successful representation of Microsoft in a major antitrust jury trial.

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 cross-border class actions and investment company and patent litigation


Intellectual Property
  • Ocado in multiple cases against AutoStore relating to patents on robots and cubic auto storage and retrieval systems
  • AB InBev and Modelo in trademark infringement and contract actions involving sales of Corona Hard Seltzer and Patagonia beer
  • Fifteen major universities in a joint patent licensing program called University Technology Licensing Program
  • 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
  • Audio MPEGPhilipsTDF, and IRT in a patent infringement action against Dell involving patents on MP-3 technology
  • Philips Electronics in multiple 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
  • MobileMedia Ideas in patent infringement actions against Apple, RIM, and HTC involving multiple patents on smartphone technology
  • General ElectricLG ElectronicsMitsubishi ElectricSamsungBTThomson LicensingColumbia UniversityPhilipsJVC, and Sony in actions against Lenovo and Haier for infringing patents essential to the MPEG-2 and ATSC digital video compression and transmission standards 
  • 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 
  • Dyson in patent and false advertising litigation concerning the design and capabilities of its vacuum cleaners, including obtaining summary judgment in two actions dismissing plaintiffs’ patent claims against Dyson
  • Labatt in a patent infringement action, including at trial, involving its patent on a method for brewing “ice” beer
  • 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
  • Abiomed in securing dismissal of all claims in a putative securities class action filed in the Southern District of New York
  • 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
  • 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
  • Banco Bradesco in a securities class action relating to Brazil’s “Operation Zelotes” tax corruption investigation
  • 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
  • Cablevision in shareholder derivative and class actions concerning options “backdating” and “going private” offers
  • Various mutual funds and their directors in investigations and civil actions concerning board decisions and fund practices
  • Ally Financial in multiple antitrust class actions relating to trading of GameStop and other stocks in so-called “short squeeze” purchases
  • Novo Nordisk in an antitrust class action alleging Novo sought to exclude generic competition for its Prandin® diabetes drug 
  • 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
  • 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
  • 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
  • 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
  • Eisai in a breach of contract action against Pfizer and Viatris relating to sales of the generic form of Lyrica® in Japan
  • 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, Penn Plaza, and Harlem Park
  • Canary Wharf in pursuing a $780 million claim in the Lehman bankruptcy
  • 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
  • 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
  • The Bank of New York in investigations and civil actions concerning the Bank’s business with certain Russian customers
  • Softbank in connection with contract, tort and fiduciary duty claims brought by a video game development company in which Softbank invested


  • Concurrences Review – Best Antitrust Business Article: Intellectual Property Category (2020)
  • New York Super Lawyers (2010, 2013-2022)
  • 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 – 2023)
  • National Law Journal – Bristol v. Microsoft named one of the “major civil-suit verdicts that beat the odds” (May 2000)