 He was also a delegate to the 11th International Student Conference in 1965 at Christchurch, New Zealand.Quisumbing became a technical assistant to Executive Secretary Rafael Salas in 1965, and then became an assistant state counsel at the Department of Justice from 1966 to 1968.After a stint in private practice from 1968 to 1983, he joined the administration of President Corazon Aquino as senior executive assistant to the defense minister in 1986 and Undersecretary for the Department of National Defense in 1987.