 He graduated from St. Mary's College (Collège Sainte-Marie de Montréal) in 1864 and received his law degree from Kentucky University (now Transylvania University) in 1869.Judge Mulligan was an editor, attorney, judge, legislator (Kentucky House 1881-1889 and Senate 1889-1893), consul-general to Samoa (1894–1896), and orator.While in Samoa, he befriended English novelist Robert Louis Stevenson.