The Waitangi Tribunal is to decide whether the Trans-Pacific Partnership (TPP) protects Maori interests.
The tribunal will spend all of next week hearing from claimants and the Crown in Wellington.
The issues for the inquiry are whether the trade deal protects the interests of Maori and what input is necessary from Maori to ratify it.
The chair of the Mataatua Maori Council, Maanu Paul, said the government had no mandate to commit Maori to an international contract
Mr Paulm, who is one of many claimants, said he would have expert witnesses supporting his position.