Barker studied at the University of Western Australia and was admitted to practice in 1973.
He practiced in Perth for several years, before undertaking postgraduate study at York University in Canada.
He returned to Australia in 1981, and was a member of the faculty of law at the Australian National University in Canberra from 1981 to 1985.
While a practicing barrister, he served a term as counsel assisting the WA Inc Royal Commission in 1991-1992, and spent four years as Chairman of the Western Australian Town Planning Appeals Tribunal from 1990 to 1994.
He is now an associate member of Murray Chambers, Barristers, Perth, Western Australia and acts as a mediator and consultant.