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Michael Attanasio

Michael Attanasio

With more than 30 years of first-chair trial experience, Mike represents Fortune 500 companies and executives in high-stakes commercial litigation, white collar investigations, and enforcement matters. He also conducts internal investigations and advises Boards of Directors on strategic responses to litigation and regulatory risk. Over the course of his career, Mike has represented some of the most prominent companies in the world, including Google, Qualcomm, Sony, Illumina, and UnitedHealthcare, as well as individuals under investigation for securities fraud, insider trading, and price-fixing. In addition to serving as a strategic adviser to several longtime clients, Mike has led teams in jury trials in state courts throughout California and in federal courts in New York, Washington, D.C., Texas, Ohio, Kentucky, and California. Frequently brought into high-stakes trials shortly before they are scheduled to begin, Mike is nationally recognized for his prowess in jury selection, cross-examination, and closing argument. He has deftly cross-examined senior executives, law enforcement agents, and expert witnesses in fields ranging from accounting and complex technology to DNA identification. In one of the defining moments of his career, Mike served as lead counsel for Jenner & Block in its challenge to a retaliatory Executive Order issued by the President. The Executive Order sought to revoke security clearances, forbid access to federal buildings, and restrict the firm’s work with federal contractors. In less than a week, Mike led a Cooley team that filed suit to enjoin the Executive Order. His widely praised arguments secured first a temporary restraining order and then summary judgment. The litigation against the Executive Orders targeting the legal industry was hailed for its success in defending the profession and the rule of law. A fellow in the American College of Trial Lawyers and a former federal prosecutor, Mike is ranked Band 1 by Chambers for Commercial Litigation and in 2026 he was recognized by the Daily Journal among its Leading Commercial Litigators in California. He has been named one of the Top 250 lawyers in America by Forbes, one of the Top 100 Lawyers in California by the Daily Journal, a “Game Changer” by The Recorder, and a “White Collar MVP” by Law360.
Sean Brownridge

Sean Brownridge

Sean Brownridge is chair of Cooley’s activism defense group and a nationally recognized activism practitioner. He is a trusted advisor to boards of directors and management teams, with a principal focus on shareholder activism preparedness and defense, investor engagement, crisis management, complex corporate governance matters and contested M&A. Sean has advised on some of the most high-profile and significant matters in the activism space, including the largest director election proxy contest in history and the biggest M&A transaction ever subject to a proxy fight. Sean brings deep experience navigating high-stakes settlements, proxy contests, withhold campaigns, short attacks and corporate crises. During his career, he has worked on activism engagements involving Avis Budget Group, Bristol-Myers Squibb, Centene, Colgate-Palmolive, Del Frisco’s, FedEx, Kellanova, Kenvue, Salesforce, Six Flags, Squarespace, Vitamin Shoppe, The Walt Disney Company and Wynn Resorts, among others. As a complement to his representations of public companies, Sean has extensive experience counseling engaged shareholders across the activism spectrum on the assessment of investment opportunities, capital deployment and investment execution, private engagement, settlement negotiations and cooperation agreements, alternative activism strategies, proxy contests, hostile takeovers and contested M&A transactions. His work with Carl Icahn, Corvex Management, D. E. Shaw & Co., Elliott Management, JANA Partners, Land & Buildings, Politan Capital Management, Sachem Head Capital Management, Starboard Value and Trian Partners – in addition to first-time and occasional activists – informs his guidance to directors and executives.