The government is confident it will be able to partially privatise Mighty River Power in April even if the Maori Council's legal challenge goes to the Supreme Court.
The council's case for a judicial review of the government's decision to sell 49 per cent of the shares in the energy company opened in the High Court in Wellington on Monday and is expected to go to appeal, regardless of the outcome.
The application forced the government to delay the share float from this month to April and Prime Minister John Key says he expects that deadline will be met.
"It will go through in time, including the Supreme Court," he said.
The council argues partial privatisation of the hydro station will compromise Maori water interests and could affect Treaty of Waitangi claims.
Helen Cull QC, counsel for the Waikato River and Dams Claims Trust and the Pouakani Claims Trust, which have joined the council in the action, told the court on Monday Maori claims to water rights could not be adequately protected because Mighty River Power had been removed from the State-Owned Enterprises Act.
However, presiding judge Justice Ronald Young said he couldn't understand her argument given legislation explicitly assured Maori that the crown would continue to be liable for the settlement of claims.
"You are really saying parliament isn't sovereign... if the statute says it's protected, it's protected," he said.
The council is due to make its submission on Tuesday, before crown lawyers respond, and the hearing is expected to conclude on Thursday with judgment reserved.
The government believes it has a very strong case and expects to win.