William Cohen, 81, passed away April 11, 2015. He was the C. Wendell and Edith M. Carlsmith Professor of Law, Emeritus at Stanford Law School. After earning his law degree at the University of California at Los Angeles (UCLA) in 1956, he clerked for U.S. Supreme Court Justice William O. Douglas. Following that he began his teaching career at the University of Minnesota Law School. Later he taught at the UCLA School of Law and Stanford Law School, where he retired in 1999. Professor Cohen devoted more than five decades to the study and teaching of constitutional law. He wrote or co-wrote five books as well as dozens of articles and essays. Professor Cohen was also a visiting faculty member at ASU, Magdalen College Oxford and the European University in Florence, Italy. His first wife, Betty, predeceased him, as did a son. He is survived by two daughters from that marriage; Nancy Mahoney Cohen, whom he married in 1976, their daughter, two grandsons, two great grandsons, two brothers and a sister. Donations may be made to the Palo Alto Family YMCA or All Saints Episcopal Church Palo Alto. A memorial service was held on April 29 at All Saints Episcopal Church, 555 Waverley St., Palo Alto, Calif.