Doubt is being cast on Ngaphui's chance of succeeding in its claim for sovereignty.
Hearings into the claim begin at Waitangi next week but AUT History Professor Paul Moon says the idea Ngaphui only gave away the right for Europeans to govern themselves is fatally flawed.
Moon says historically they may be right, but constitutionally they are wrong.
He says treaties evolve over time and what the tribe is missing is the fact sovereignty now rests with the Crown.
"What applied in 1840 has long since been displaced by new arrangements regarding sovereignty," says Moon.
He says Ngapuhi is unlikely to be able to take the claim much further because the tribe has misunderstood how treaties work.
"The best possible outcome would be a symbolic acknowledgement of Ngapuhi's traditional sovereignty, but otherwise, the status quo would prevail."
In 2002, Moon published the book The Path to the Treaty of Waitangi, on which some of Ngapuhi's main arguments for sovereignty are based.
And Northland Maori are pushing for a special economic development tax as part of their Treaty settlement.
Ngapuhi want to impose a 9% "tribal tax" on everyone who lives in the region, to be administered by Inland Revenue.
Matarahurahu hapu chairman David Rankin says it's a non-negotiable element of any settlement Ngapuhi reaches with the Crown.
He says the tax would help restore fiscal equity in Northland.