A law lecturer believes iwi definitely have a case if they choose to pursue legal action over partial asset sales legislation.
Jacinda Ruru from Otago University says water rights remain an unresolved issue.
Ruru told TVNZ's Breakfast this morning Maori have a right to water governance - outlined in common law - but politicians had been unwilling to formally define the "difficult, thorny" issue.
"It's interesting we have John Key saying there is nothing to litigate here when we have a Cabinet paper of only about two years ago describing Maori rights to water as undefined and unresolved," said Ruru.
"It's definitely something that needs to go through our court or our tribunal."
The Mixed Ownership Model bill allows the sale of minority holdings in four state owned enterprises but the sale of state-owned energy companies could be held up by iwi demanding compensation.
Prime Minister John Key said there is no merit to any litigation and the issues of water have been "well and truly covered off".
Ngati Tuwharetoa owns lake beds and rivers from which Mighty River power draws water and says it wants compensation from the sale of the shares.
The Government has confirmed it could hold back some Mighty River Power shares to give to the iwi as part of a future treaty settlement.