Mr. Collins joined Shearman & Sterling in 1978. In 1981, he resigned from the firm to serve as a White House Fellow and Special Assistant to then-Vice President George H.W. Bush. Thereafter, Mr. Collins served as a special assistant and later as Deputy Assistant Attorney General in the United States Department of Justice Antitrust Division under William F. Baxter. He returned to the firm in 1983. Between 1991 and 1995, Mr. Collins was an adjunct faculty member at Yale Law School, where he taught the main antitrust course as well as several specialized antitrust courses. In January 2010, Mr. Collins returned to teaching antitrust law as an adjunct professor of law at New York University School of Law.
Mr. Collins is active in scholarly programs regarding the design and implementation of competition law. He conceived and served as editor-in-chief of Issues in Competition Law and Policy, a three-volume treatise that comprehensively surveys the issues facing modern competition law in the United States, Europe and around the world. He is also the author of a book-length chapter on merger antitrust law in the Antitrust Adviser, which is the most comprehensive treatment of the subject available. As well as lecturing in the United States, Mr. Collins has lectured at the invitation of the Chinese and Russian governments in Beijing and Moscow and at academic conferences around the world.