"William Stallings is an ‘energetic and smart’ lawyer, according to respondents who effuse he is 'persuasive in front of agencies in M&A-related matters’"

Who’s Who Legal


William H. Stallings is a partner in Mayer Brown's Washington DC office, where he co-leads the firm’s global Antitrust & Competition practice. Bill’s competition and consumer protection practice covers domestic and global merger reviews, government investigations, cartels, litigation (including class actions), and government procurement matters. He regularly appears before the U.S. Department of Justice and the Federal Trade Commission. 

Before joining Mayer Brown in 2015, Bill spent 17 years at the US DOJ’s Antitrust Division, where he held several key roles, including Chief of the Transportation, Energy, and Agriculture Section. Bill had responsibility for second request merger reviews, civil conduct investigations, and litigating cases in industries such as airlines, oilfield chemicals and services, meatpacking, shipping, agricultural products, energy generation and distribution, and financial services. 

For his outstanding service in antitrust enforcement, the DOJ awarded Bill the prestigious Neil E. Roberts Award (2015). Bill is a Chambers-ranked attorney in competition law and, in 2016, the National Law Journal recognized him as an Antitrust Trailblazer. 

Since joining Mayer Brown, Bill focuses on M&A and litigation. He is recognized for providing straightforward antitrust advice and creative solutions. His high-profile client matters include:

  • securing antitrust clearance for waste hauling company in its $4.6 billion acquisition – the U.S. Dep’t of Justice described the deal as “the most significant consolidation” in the industry in over a decade and the successful resolution involved complex consent decree provisions negotiated with DOJ and numerous state attorneys general;
  • serving as lead antitrust counsel in a multibillion-dollar airline merger that successfully closed following a DOJ second request investigation and private litigation;
  • defending agricultural companies in multiple major class-action antitrust cases, including securing dismissal of one action on the pleadings;
  • representing a complainant in successfully advocating to the government that it should challenge a merger in the technology sector;
  • obtaining a favorable resolution (with no indictments) on behalf of a foreign company accused of criminal cartel, civil bid rigging, and government contracts fraud allegations; 
  • securing a no-action letter in a major FTC consumer protection investigation; and
  • representing numerous companies in obtaining early resolution of M&A merger reviews by the DOJ and FTC.

Bill is active as a Non-Governmental Advisor (on behalf of the US DOJ) to the International Competition Network (ICN), an international organization of more than 100 competition agencies with the common aim of addressing practical antitrust enforcement and policy issues.

He also serves as co-chair of the Antitrust, Competition and Consumer Protection Committee of the American Bar Association's (ABA) Air & Space Forum and is a leader of Mayer Brown's Aviation industry group, which counsels airlines, airports, and investors in navigating complex competition issues in the aviation sector. 

Learn more about the high-profile and precedent-setting matters Bill handled during his DOJ career. 

Mayer Brown Quarterly Review: M&A, Activism and Corporate Governance


At Mayer Brown

  • Represented Advanced Disposal Services in its $4.6 billion acquisition by Waste Management. The US Justice Department’s Antitrust Division and a number of state antitrust enforcement agencies investigated the deal, with DOJ describing it as presenting “the most significant consolidation in the waste industry in over a decade.” Bill handled the investigations on behalf of ADS and was heavily involved in negotiating consent decrees that resolved all competition issues to allow the deal to close.
  • Advised Dow Inc. on antitrust issues relating to its agreement to divest certain US Gulf Coast marine and terminal operations and assets to Vopak Industrial Infrastructure Americas, a joint venture of Royal Vopak and BlackRock's Global Energy & Power Infrastructure Fund, for $620 million.
  • Lead antitrust counsel to Virgin America in its multibillion-dollar acquisition by Alaska Airlines in 2016, creating the fifth-largest airline in the United States. Bill advised Virgin America on the antitrust considerations relating to the sale, represented the company before the US Department of Justice's (DOJ) Antitrust Division throughout the department's second request review and handled private litigation that threatened to derail the transaction. 
  • Represented Foster Farms in connection with a Federal Trade Commission (FTC) investigation of whether certain statements on product labels were unfair or deceptive. After an extensive investigation, including Mayer Brown white papers and other submissions, the FTC issued a public closing letter in which it declined to take action.
  • Provide antitrust advice to YUM! Brands, Inc. (KFC, Taco Bell and Pizza Hut) in connection with various matters, including its acquisition of Habit Restaurants, Inc.
  • Represent Hanjin Transportation Co. Ltd. in connection with investigations by the US Department of Justice (DOJ) into allegations of a bid-rigging conspiracy that targeted US military bases in South Korea. Negotiated favorable monetary settlement that resolved all criminal and civil claims.
  • Represented Caesars Entertainment in connection with various antitrust matters before the Federal Trade Commission, including obtaining Hart-Scott-Rodino merger clearance for its $1.7 billion acquisition of Centaur Holdings, LLC.
  • Represented SCANA Corporation, an energy-based holding company, on antitrust issues in its $14.6 billion merger with Dominion Energy, Inc. 
  • Represented a complainant in successfully advocating to the government that it should challenge a merger in the technology sector;
  • Defending poultry, pork and turkey companies in multiple class-action price-fixing cases;
  • Advised numerous domestic and global companies on the antitrust implications of potential transactions under consideration.
  • Represented companies in federal court and before the DOJ and FTC in merger and competition-related proceedings. 

While at DOJ

  • Developed the legal precedent in the KeySpan and Morgan Stanley cases for holding financial institutions liable for Sherman Act violations arising from the use of derivative agreements.
  • Obtained, for the first time, disgorgement of ill-gotten gains as a remedy for Sherman Act (KeySpan) and Clayton Act (New York Tour Buses) violations.
  • Led the Antitrust Division’s investigation of US Airways’ acquisition of American Airlines, which resulted in the divestiture of an unprecedented number of slots and gates at some of the most important US airports.
  • Directed the Antitrust Division’s investigation of the merger of National Cinemedia and Screenvision, the two top US cinema advertising networks. The parties abandoned the transaction shortly before trial.
  • Managed the Antitrust Division’s successful challenge of the JBS/National Beef merger.
  • Served as a key member of the successful trial, appellate and judgment compliance teams in United States v. Visa.


University of North Carolina at Chapel Hill, BA

University of North Carolina School of Law, JD


  • District of Columbia