The High Court judge hearing a challenge against the Government's Three Waters by the Whangārei District Council has reserved her decision.
Justice Jill Mallon has reserved her decision in the case brought by the Whangārei District Council (WDC) with the Timaru and Waimakariri District Councils against the Government, seeking independent declarations related to property ownership rights.
The matter was heard in the court on Tuesday and Wednesday this week and the decision will be released at a later date.
Whangārei Mayor Sheryl Mai said the future of her district's $1.34 billion of ratepayer-funded drinking water, stormwater and wastewater assets rested on the decision.
She said the independent declarations sought were about clarifying fundamental principles of property ownership and democracy.
Councils around New Zealand are watching the outcome of the High Court case, held in Wellington on Tuesday and Wednesday.
Mai said the ownership and property rights of councils' Three Waters assets were at stake.
The High Court declaration will likely have ramifications for all New Zealand councils.
A ruling in favour of what the councils say is the traditional view of "ownership" will likely open the Government up to having to pay the council's compensation for their Three Waters assets.
In June last year, WDC became the first in New Zealand to opt out of the Three Waters restructuring which aims to combine 67 councils' drinking water, wastewater and stormwater functions into four new separate entities.
In the north of New Zealand, this would see those assets from WDC, the Far North District Council, the Kaipara District Council and the Auckland Council shifted under the control of one of four giant inter-regional water services entities.
The top-of-New Zealand water services body founded on the four councils' assets would be known as entity A.
■ Local Democracy Reporting is Public Interest Journalism funded through NZ On Air.