The 1932 deed calls the relevant people representative members of the Board. It describes the capacity attached to each position: a family, a population, a locality, or a region. The Board's legal job was to administer the Waitangi trust estate. The deed does not confer legislative, judicial, taxing, policing or territorial-government powers on those representatives.
A person can represent a territory without governing that territory. The legal power must come from the instrument, not from the geographic label.
Lord Bledisloe's own public letter is unusually helpful. He said he wanted trustees drawn from Government, the Māori race, the immediate locality, the South Island, and the Williams and Wakefield families in order to emphasise the national character of the memorial and help heal historic controversy. That is direct evidence of representational design.
The first seven family/territorial positions were: Kenneth Stuart Williams for the Henry Williams family; Riri Maihi Kawiti for the Heke, Kawiti, Nene and Pōmare families; Tau Hēnare for Māori in the North Auckland Peninsula; Te Rata Mahuta for Māori in the North Island south of Auckland; Vernon Reed for Bay of Islands Pākehā; Heaton Rhodes for Māori and Pākehā of the South Island; and Dillon Bell for the Wakefield family. Coates was an eighth, different at-large position for a person prominent in national life.
A 1934 account described Waitangi as belonging to Pākehā and Māori, North and South Islanders, with the different historical sections represented on the Board as part of a wider project of national unity. That evidence makes the “representative national memorial” explanation much stronger than a theory of seven delegated governments.
Finding: the seven positions were legally differentiated trustee offices. Not proved: that any of them held sovereign or governmental jurisdiction over the people or territory named in their representative capacity.
Primary sources: Waitangi National Trust Board Act 1932 and Schedule 1 deed; Bledisloe's 10 May 1932 letter as published in the Otago Witness; Waitangi: Ninety-Four Years After (1934).