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.