The Supreme Court has agreed to hear an appeal to decide which of two competing interests can take water for irrigation from the Rakaia River in Canterbury.
There has been a protracted legal wrangle involving dairy company Synlait and the Central Plains and Ashburton Water trusts.
The Environment Court initially ruled in favour of Central Plains, but that was overturned by the High Court, then reversed again by the Court of Appeal, which said the water should go to the first fully-completed application to the regional council.
The Court of Appeal judges also noted that a stand-alone regime for allocating water resources was a matter for Parliament, not the courts.
The Supreme Court has now given Synlait leave to appeal against that ruling.