Mr McIntyre is a Life Member and Past-President (2019) of the Law Society of WA and Chairs its Human Rights and Equal Opportunity Committee and Indigenous Legal Issues Committee and is a member and former Convenor of its Access to Justice Committee. He Chairs the Board of Directors of Law Access Ltd, a pro bono legal referral service of which the Law Society of WA is the sole shareholder. He is also a Vice-President of the International Commission of Jurists, Australian Section and President of its WA Branch. He is a Western Australian Patron of the Justice Reform Initiative which advocates for alternative forms of criminal punishment to incarceration.

Mr McIntyre was admitted to practice as a Barrister, Solicitor and Proctor of the Supreme Court of Western Australia in 1976. He went to the Independent Bar in Western Australia in 1993 and was appointed Senior Counsel in 2002. His early years of practice were with Aboriginal and Torres Strait Islander Legal Services in Western Australia and Queensland. He had the conduct of the High Court of Australia case of Mabo v Queensland from its inception in 1982 until its conclusion in 1992 and his practice has since included many native title cases.

He also had the conduct of the High Court of Australia case of Koowarta v Bjelke Petersen in 1982 which determined that the Racial Discrimination Act was a valid exercise of the external affairs power of the Commonwealth of Australia. His practice has since included racial discrimination cases (including racial vilification cases) and sexual discrimination, sexual harassment and disability discrimination cases. He argued the case of Bropho v Western Australia in the High Court of Australia in 1990, which established that the Crown was bound by the Aboriginal Heritage Act 1972 (WA). His practice has included many cases concerning Aboriginal cultural heritage protection and some concerning environmental protection. He argued the cases of Bodney v Federal Airports Commission and Collard v WA seeking to establish that the Crown owed a fiduciary duty to Aboriginal people.

He was awarded the Australian Human Rights Commission Law Award in 2009.