He teaches public international law and his research focuses on regime change and state responsibility. He previously clerked at the International Court of Justice for President Hisashi Owada and Judge Giorgio Gaja.Professor Butler holds a B.A. in History from Harvard University, a B.A. in Jurisprudence from Oxford University and a J.D. from Yale Law School. He is a member of Phi Beta Kappa, a Rhodes Scholar and a member of the New York State Bar.