Donald Ayer is a retired partner in the Washington D.C. office of Jones Day. He has argued 19 times in the U.S. Supreme Court, more than 70 cases in the intermediate appellate courts, and has also been lead counsel in approximately 20 trials, most before juries. He received an A.B., with Great Distinction, from Stanford in 1971, an M.A. in American History from Harvard in 1973, and a J.D. from Harvard in 1975, where he was Articles Editor of the Law Review. He clerked for Judge Malcolm R. Wilkey of the D.C. Circuit, and for Justice William H. Rehnquist.

Professor Ayer has served since 2006 as an adjunct professor teaching a course in Supreme Court Litigation at Georgetown Law School. He is presently a member of the Council of the American Law Institute, and Chair of the Publications Committee of the Supreme Court Historical Society. He has served previously as President of the American Academy of Appellate Lawyers and of the Edward Coke Appellate Inn of Court.

Before entering private practice in 1990, Professor Ayer spent ten years in the United States Department of Justice, including two Presidential appointments. He worked in California first as an Assistant U.S. Attorney, and from 1981-1986 as United States Attorney in Sacramento. In 1986 he moved to Washington as Principal Deputy Solicitor General under Solicitor General Charles Fried, during the final three years of the Reagan Administration. In 1989, he was appointed by President George H.W. Bush and served as Deputy Attorney General during 1989-1990.

Since his retirement from Jones Day in 2018, Professor Ayer has written extensively on rule of law issues, including many articles addressing the abuses of our legal system perpetrated by the Trump administration.