In 2003, Kerr took a leave of absence from the law school to clerk for Justice Anthony M. Kennedy of the United States Supreme Court during October Term 2003.[5] In 2009, he served U.S. Senator John Cornyn of the Senate Judiciary Committee as Special Counsel for Supreme Court Nominations during Sonia Sotomayor's confirmation as Supreme Court Justice;[6] a year later, he again served as an advisor to Cornyn, this time on the Supreme Court confirmation of Elena Kagan.[7]