South Africa’s High Court upheld a legal challenge to the government’s plan to procure 1 500 megawatts of new coal-fired power, ruling that it was unlawful because of the potential impact on public health.

Plans for more electricity from the dirtiest fossil fuel in South Africa, which has the most carbon-intensive economy among the Group of 20 nations, violate the constitutional right to health, Judge C.J. van der Westhuizen wrote in a ruling released on Wednesday.

Three environmental activist groups filed the case against South Africa’s energy minister and energy regulator as well as President Cyril Ramaphosa after the government disclosed its intentions in a 2019 energy plan that the ministry approved in 2020.

Those decisions are “unlawful and invalid”, the judge said, ordering the minister and regulator to pay costs to the complainants.

This is another victory for activists in the country who have already won rulings stating that the government needs to enforce laws designed to limit pollution from burning coal and blocking some offshore oil exploration.

Still, South Africa relies on coal for about 80% of its power and has some of the world’s worst air quality. Pollution from the fuel causes ailments ranging from respiratory illness to strokes and heart attacks with the state power utility, Eskom, admitting its emissions kill hundreds of people annually.

When the case was first filed, Energy Minister Gwede Mantashe said that securing the right to use coal for new power plants was worth a court battle.

Even so, South Africa is pressing ahead with plans to reduce its reliance on coal by ordering additional renewable energy and implementing a $9.3-billion climate finance pact with some of the world’s richest nations.

Mantashe and some other politicians have argued that the switch to clean electricity will jeopardise energy security and could cost tens of thousands of jobs that depend on the mining and burning of coal.