He replaced Glenn Joyal, who was appointed a judge of the Court of Queen's Bench.
In 1978, he was appointed a part-time judge of the Provincial Court of Manitoba, working in the Criminal Division.
MacInnes has heard cases and written decisions arising out of civil and criminal law trials.
He has also served as the Secretary of the Canadian Superior Courts Judges Association.
Before his appointment to the Bench, he was a frequent speaker, lecturer and prominent member of the Law Society of Manitoba, the Federation of Law Societies of Canada and several charitable foundations in Winnipeg.