In her first case after starting her own legal practice, she represented Phyllis Naidoo who was charged for failing to report to the police station as a banned person. In 1971, she represented 10 members of the Unity Movement who were charged under the Terrorism Act. Pillay also represented her husband Gaby Pillay who was detained by the Security Police under Terrorism Act. It was at this time that exposed the practice and effects of torture and solitary confinement on detainees held in police custody. In 1973, she fought and won the right for political prisoners to have access to legal counsel. In the mid 1970s, Pillay defended detained members of the Black Consciousness Movement (BCM) such as Saths Cooper and Strini Moodley. Pillay later became the first woman to open legal practice in Durban.
In 1982, she obtained a Master of Law and in 1988 a Doctor of Juridical Science from Harvard University. In 1995, Pillay joined the International Criminal Tribunal for Rwanda, and in 1999 she was elected as its Judge President for which she served two four-year terms. Since 2003, she has served as judge on the International Criminal Court. Pillay is cofounder of the South African Advice Desk for Abused Women and was appointed the United Nations High Commissioner for Human Rights on 28 July 2008.
