He holds undergraduate degrees in Arts (History) from the University of Sydney and Law from UNSW, and a PhD from UNSW. Prior to embarking on an academic career, Greg practiced as a solicitor in the litigation group of a large national firm. He has taught law at UTS, the University of Sydney and most recently for six years in the UNSW Faculty of Law. He is widely recognised as an expert in administrative law and is an author of many publications in that and related areas, including a monograph entitled Soft Law and Public Authorities: Remedies and Reform (Hart Publishing, 2016) and, with Mark Aronson and Matthew Groves, the leading Australian administrative law text, Judicial Review of Administrative Action and Government Liability (Thomson Reuters, 6th ed, 2017).