 Mildren was President of the Northern Territory Law Society from 1973–75 and 1979–81.He was also Deputy Chairman of the Northern Territory Legal Practitioners Complaints Committee from 1983–88, Chairman of the Northern Territory Planning Appeals Committee from 1979–85, Chairman of the Northern Territory Council of Law Reporting from 1993–95 and President of the Northern Territory Law Reform Committee from 1991–97.He is a life member of the Criminal Lawyers Association of the Northern Territory.