He is a graduate of the Australian National University and Harvard Law School and was a barrister in private practice before his appointment as solicitor-general.

[5] Gageler represented, among others, Betfair, the Humane Society, the ACT Government, and John Howard (the Prime Minister of Australia).

[7] Gageler was appointed the Solicitor-General of Australia on 1 September 2008,[5] based in Canberra, Australian Capital Territory.

This position is the second law officer of the Commonwealth, advising the Government and appearing as counsel in significant cases.

Gageler defended the Commonwealth unsuccessfully in the Malaysian solution challenge and successfully in the tobacco plain packaging cases in 2012.

On 22 August 2023 the Federal Government announced that Gageler would succeed Susan Kiefel as Chief Justice of the High Court upon her retirement at the end of the year.

The painting depicts the High Court sitting on Tuesday 29 April 2003 to hear the case Purvis v State of New South Wales [2003] HCA 62.