In a landmark victory for Indonesian environment campaigners, a court on September 16 ordered President Joko “Jokowi” Widodo to clean up Jakarta’s notorious air pollution, ruling that the leader and other top officials had been negligent in protecting citizens.

The capital and its surroundings form a megacity of about 30 million people, which routinely ranks among the most polluted cities in the world.

Experts have warned for years about the threat posed by Jakarta’s smog to the health of residents, especially children.

A group of 32 activists and citizens impacted by pollution had filed the lawsuit two years ago, accusing Jokowi, as well as his ministers for health, home and environment, and the governor of Jakarta, of negligence over the state of the city’s environment.

The officials were found to have “violated the law”, presiding judge Saifuddin Zuhri of the Central Jakarta District Court said, ordering them to tighten environmental regulations and enforcement.

They asked the officials to especially crack down on the pollution generated by vehicles and the coal-fired power plants around Jakarta, including with sanctions for violations.

The judges also told authorities to improve air monitoring systems and make pollution data public.

The petitioners had not asked the court for any monetary compensation.

Ayu Eza Tiara, a lawyer for the plaintiffs, said that the defendants must accept their “defeat” and comply with the ruling.