South Africa's top court ruled on Thursday that a platinum miner that has a deal with a tribal chief could not evict a group of black farmers, in a decision that could curtail the power of traditional leaders whose deals often disadvantage poor blacks.

Land rights are a red-hot issue ahead of elections in 2019 as the African National Congress (ANC) moves for constitutional change aimed at a more equitable distribution of land.

This includes expropriating land from whites without compensation, but also addressing the plight of poor blacks vulnerable to forced evictions in tribal lands because of deals stuck by local chiefs under a property rights system with roots in the colonial and apartheid eras.

At issue in the case before the Constitutional Court was a deal agreed with the council of the Bakgatla tribe to allow Pilanesberg Platinum Mines (PPM), a unit of unlisted Sedibelo Platinum Mines, to evict farmers to expand its open-pit mine.

The farmers argued that they were the rightful owners of the farm and needed to be consulted before mining took place.

In previous court filings, PPM and a partner company formed by the tribal council took the position that the Bakgatla community controls the farm and adjoining properties communally, with the chief as custodian.

The court ruled that such an arrangement ran rough shod over the rights of the applicants, comprised of 13 families whose ancestors bought the farm over a century ago but could not get title deeds to it because of racist laws at the time.

"There is a constitutional imperative ... to ensure that persons or communities whose tenure of land is legally insecure as a result of past racially discriminatory laws or practices are entitled either to tenure which is legally secure or to comparable redress," it said.

After the unanimous judgment was delivered, about 50 people including the farmers facing eviction and their supporters broke out into song and dance in the court.

"We feel vindicated. The chief never listened to us," said a jubilant Setshedi Rasepae, one of the supporters.

Through a spokesperson, the company said: "Sedibelo Platinum Mines is studying the judgment and will advise pursuant actions as and when appropriate."

Lawyers and land policy experts say the implications are far reaching and could raise questions about other mining deals signed between companies and tribal chiefs, which have stoked social strife and conflict.

"It dramatically undermines the powers of traditional leaders to make deals on behalf of subjects," said Johan Lorenzen, a lawyer at human rights firm Richard Spoor Inc Attorneys.

Aninka Claassens, director of the University of Cape Town's Land and Accountability Research Centre, said: "No mining company can continue to pretend that traditional leaders are authorised to make these deals without the consent of the people directly affected."

Traditional leaders hold sway in South Africa's old "Homelands," islands of rural poverty where most blacks were literally confined along tribal lines under apartheid.

These areas comprise only 13 percent of South Africa's land but are home to a third of the population, 17-million blacks, mostly subsistence farmers working tiny plots.

On these lands, the chiefs often determine who gets to farm or where cattle are grazed and also - and more significantly - who gets access to resources like water and minerals.

The chiefs maintain they are the custodians of African culture and tradition and play a role in mediating disputes and dispensing justice among their subjects. Critics allege some have used their powers of resource allocation to enrich themselves.