At least 10 groups from iwi around the country have asked to join a Waitangi Tribunal claim challenging New Zealand's involvement in the Trans Pacific Partnership (TPP) agreement.
Claimants, including Moana Jackson, Hone Harawira, Angeline Greensill and Moana Maniapoto lodged the initial application for an urgent hearing on the issue last month.
The lawyer for the Tai Tokerau District Maori Council, Gerald Sharrock, said the council was worried the TPP could constrain the powers of the tribunal itself, and its power to assign guardianship over indigenous flora and fauna.
But he said the underlying issue was the country's autonomy and sovereignty.
Mr Sharrock said the Government's secrecy over the deal flouted the fundamentals of the Treaty of Waitangi and there was a serious question as to the power of the Crown to enter into the TPP without engaging its treaty partners.
The council believed the Government should also be consulting Pakeha citizens about the TPP, but Mr Sharrock said the Government was opposing its request.
The Crown had told the Waitangi Tribunal an agreement on the TPP could be reached this month, and there was no realistic window of time for an inquiry.
It said the Government had the kawanatanga [governorship] to make foreign policy under Article 1 of the treaty and it had taken reasonable steps to inform itself of Maori interests.
The Crown said a robust Treaty of Waitangi exceptions clause was in all New Zealand free trade agreements, and it protected the Crown's ability to meet its treaty obligations.