Matanuku has been in corporate and private practice since 1991, and co-founded Kāhui Legal in 2003. Prior to establishing Kāhui Legal, Matanuku was a partner at Walters Williams & Co and in-house counsel at the Treaty of Waitangi Fisheries Commission.
Matanuku provides advice on a wide range of corporate, commercial, Treaty settlement and public law issues. Matanuku has acted on a large number of Treaty of Waitangi settlements, represented Ngāti Porou throughout their foreshore and seabed negotiations, and in 2012 was the Chair of the Ministerial Panel on the reform of Te Ture Whenua Maori Act 1993. He has also acted as a Treaty of Waitangi settlement negotiator and has worked directly on various items of law reform.
Matanuku has held a wide variety of board roles including being the former Deputy Chair of Aotearoa Fisheries Limited (now Moana New Zealand) and the Chair of Sealord Group. He is currently the Chair of the Ngāti Porou Holding Company and holds a number of other directorships.
Matanuku lives in Gisborne. He is married to Tiana (who is also a lawyer) and has three children.