In 1987 he co-founded Ngā Kaiwhakamarama i Ngā Ture (the Māori Legal Service). He also supported the rights of indigenous people internationally – for example, through leading the working group that drafted the United Nations Declaration on the Rights of Indigenous Peoples and sitting as a judge on the International Tribunal of Indigenous Rights in the 1990s.
In 1987, he established Ngā Kaiwhakamarama i Ngā Ture (the Māori Legal Service) to champion the rights of indigenous people globally, notably by leading the drafting committee for the United Nations Declaration on the Rights of Indigenous Peoples and serving as a judge on the International Tribunal of Indigenous Rights in the 1990s.