Lawyers for water claimants will pick over the principles of the Treaty of Waitangi when their case goes to the Supreme Court on Thursday.
The hearing follows a ruling from the High Court that there was no connection between the sale of shares in state-owned hydro generator Mighty River Power and the need to provide for Maori claims to water.
The argument for the recognition of Maori interests in freshwater has also been before the Waitangi Tribunal.
A group of Waikato Maori trusts is taking the action, led by Tamati Cairns, chairman of the Waikato River and Dams Claims Trust and Pouakani Claims Trust.
At Thursday's hearing there will be particular focus on the principle of partnership between Maori and the Crown which requires both sides to act reasonably and in good faith.
Mr Cairns says his people are still firm in their position that the Crown is not acting according to the principles of the Treaty of Waitangi.
He says the power scheme sell-off needs to be blocked until Maori rights are acknowledged.
Mr Cairns says the Government's plan to sell nearly half of some state owned hydro power stations means the water's also being sold.
The Government plans to offer shares in up to 49% of Mighty River Power in the first half of this year, if the Supreme Court's decision goes the Crown's way.
Meanwhile, Maori Council deputy chair Rahui Katene says although it's a day for the lawyers, there will be a degree of support from tangata whenua.
She says council committee members and Maori wardens from Wellington have signalled they want to attend the case.
Ms Katene says although the Supreme Court will be hearing technical arguments, the water hearing is about the people and how the use of water will affect their lives.
A new legal team will lead the case, headed by commercial and corporate lawyer Colin Carruthers QC.