The Government could face a decade-long battle over Māori rights to freshwater, a conflict with potential to become as difficult as the controversial Foreshore and Seabed Act.

Some legal minds are saying Māori are entitled to ownership of water - including the right to restrict others' use, and to compensation for unpaid royalties.

Darrell Naden of Tamaki Legal told Newshub denying Māori ownership to water is akin to the confiscation of land by early Pākehā settlers.

"The taking of another set of property interests in a natural resource like freshwater shouldn't be tolerated. In terms of getting complex or even dramatic, I'd say that's on the cards," he said.

"Frustration is putting it mildly. It's raupatu - theft - at heart," Mr Naden said.

Regional Development Minister Shane Jones said the Government could face a decade in court.

"I'm deeply fearful of another 10 to 15 years of litigation," he said on Tuesday.

"It takes a long time to work iwi by iwi, hapū by hapū, which is why that's one Pandora's box I want nothing to do with opening up," Mr Jones said.

A former Māori MP told Newshub the water ownership issue could easily become as fraught as the Foreshore and Seabed Act 2004, which was a huge challenge for the previous Labour Government.

It was divisive to the point that Tariana Turia resigned from the Labour Party, forming the Māori Party alongside academic Pita Sharples.

The Government's position is that no one owns freshwater, and it belongs to everyone. Almost the same position - that no one owns water - was taken by the previous Government.

Mr Naden said Māori should seek to protect rights over the resource, and that's likely to happen through the courts.

"We think we'll end up in court. Based on current case law, we think we'll prevail," Mr Naden said.

"The Crown will want to legislate that court victory away. That kind of thing's happened in the past."

He said acknowledging Māori rights could mean compensation for unpaid royalties and Māori governance over water use and discharges. He said to his clients, it's less about direct monetary gain and more about having governance over the resource.

Water is "one of the last resources that might assist with getting Māori off the bottom rung of the ladder", Mr Naden told Newshub.

The Crown released its water policy earlier this month, but it avoids dealing with the question of ownership, instead focusing first on cleaning up rivers, and then looking into the more difficult issue of water allocation.

Government Cabinet documents released alongside the water policy plans warn water allocation is "not straightforward". "Many of these issues cannot be resolved without substantial discussion with Māori," the documents say.

The papers also warn dealing with the question of ownership through the courts would be expensive, result in "long delays", the "continuation of economic inefficiencies", and patchwork rules across the country.

None of the parties involved want to go through the courts, but if the Government can't come to an agreement that satisfies Māori on water rights, it risks a repeat of the last Labour Government's conflict over Māori rights - the Foreshore and Seabed Act.

Newshub.