A hunting and fishing lobby group says it will ask the High Court to decide whether Crown leases to high country farmers were only meant to be for grazing.
Fish and Game is challenging the right of pastoral lessees to restrict access to their properties.
It plans to seek a judicial declaration that the farmers were never intended to have extended property rights - such as the right to keep members of the public off the Crown land.
For more than 100 years, farmers have been able to pay low rentals to use crown land in the iconic South Island high country for grazing, with restrictions against use of the land for other purposes such as tourist resorts, subdivision, or forestry.
"Pastoral leases have probably been talked-up to be more than what they are," Fish and Game chief executive Bryce Johnson told NZPA .
"A pastoral lease only gives a right to the grass - but nothing else. It doesn't attract the provisions of the Trespass Act, so it doesn't give exclusive occupancy. "It's a statutory lease, not a common lease, so if it only says you have exclusive right to the pasturage, then that's it ... it doesn't say you have exclusive occupation".
"From a public access point of view, we're hugely interested in that. It could be a good outcome for the public."
If a court agreed with the Fish and Game application Mr Johnson said he expected that the decision would be appealed.
He did not know what effect any judgment might have on the deals the Government has already done to give leaseholders freeholdings on land valued as though they had a wider property right than simply control of the grazing.
Fish and Game will rely heavily on research by Dr Ann Brower, a lecturer in public policy at Lincoln University, who is writing a book on the leases: Who Owns the High Country?
Dr Brower has extensively researched the Government's tenure review policy, which has paid out over $18.5 million to leaseholders during the past 15 years and is expected to pay out another $9 million this year.
The reviews, under the Crown Pastoral Land Act have allowed pastoral leaseholders to freehold "commercial land" by transferring areas with high conservation, or Maori or historic values to the Crown.
Lessees negotiate with the government the right to freehold part of their pastoral lease in return for surrendering land of conservation value.
But Dr Brower has alleged large areas of high country have been sold off to runholders for knock-down prices, in a process hidden from public view.
Some high country farmers have made windfall gains at the public's expense by freeholding leases valued as grazing land, and then selling it as lifestyle blocks around Lake Tekapo, Wanaka, Hawea and Wakatipu, and in some of the finest vineyard country in Central Otago.
According to Dr Brower, about 20 percent of the available privatised land has been onsold for about $122 million. In the past two years, the Government has introduced new "landscape" covenants on newly privatised land that prohibits most development and all subdivision.
Federated Farmers' high country chairman, Donald Aubrey said he believed the court action was to gain access to privately held land for Fish and Game members.
Farmers with pastoral leases had the right to exclude others, just like a tenant in a rented house.
"It is not practical to farm anywhere if farmers have no control over livestock or their land," Mr Aubrey said.