On completing his Leaving Certificate in 1952[5] Barker chose to qualify in law through the NSW Solicitors Admission Board.

Barker also successfully defended High Court judge Lionel Murphy from a charge of perverting the course of justice.

[2] Barker was a member of the International Human Rights Observer Panel which was established in 2005 by the Law Council of Australia.

It was a part-time panel of Australian lawyers who serve as trial observers and undertake reviews in relation to human rights.

[10] He was regularly called upon by the national media as a commentator on matters relating to human rights and civil liberties.