Slattery graduated from the [[University of Sydney]] with degrees in [[Bachelor of Arts|arts]] (1975) and [[Bachelor of Laws|law]] (1977). He became a [[barrister]] in 1978, [[Queen's Counsel]] in 1992 and justice of the [[Supreme Court of New South Wales]] in 2009. He joined the [[Royal Australian Navy Reserve]] as a Lieutenant in Supply Branch – Legal in 1990. He rose through the ranks and was appointed Judge Advocate General – Navy (as [[Commodore (rank)|commodore]]) in 2010 and Judge Advocate General – ADF (as [[rear admiral]]) in 2014.<ref>{{cite web |url=http://www.navy.gov.au/biography/rear-admiral-michael-john-slattery |title=Rear Admiral Michael John Slattery |publisher=[[Royal Australian Navy]] |accessdate=11 June 2019}}</ref>
Slattery washas been appointed a [[Member of the Order of Australia]] (AM) twice: he was appointed in the Military Division in the [[2019 Queen's Birthday Honours (Australia)|2019 Queen's Birthday Honours]] for his "exceptional service" to military law".<ref>{{Cite It's an Honour |ausawardid=2004896 |recipient=Rear Admiral the Honourable Justice Michael John SLATTERY RAN |award=Member of the Order of Australia |postnominal=AM |citation=For exceptional service in the field of military law, particularly as Judge Advocate General of the Australian Defence Force. |accessdate=11 June 2019}}</ref> In the [[2022 Australia Day Honours]], Slattery was again appointed a Member, this time in the General Division, for "significant service to the law, to the judiciary, and to professional legal associations".<ref name="2022 Honours SMH">{{cite news |title=Australia Day 2022 Honours List |url=https://www.smh.com.au/national/australia-day-2022-honours-list-20220125-p59r53.html |access-date=25 January 2022 |work=Sydney Morning Herald |publisher=Nine Entertainment Co |date=25 January 2022}}</ref>
