The U.S. Supreme Court has rejected a request from ExxonMobil to overturn a historic ruling allowing ordinary people and citizen groups to sue industrial polluters, upholding what legal experts say is a crucial mechanism to deter companies from continuously breaking environmental laws.

The decision concludes more than a decade of litigation over toxic pollution from Exxon’s petrochemical complex in Baytown, Texas. In 2010, environmental groups sued Exxon on behalf of residents living near the facility for years of reported violations of its Clean Air Act permits, including pollution of cancer-causing chemicals. A federal judge hit the company with a nearly $20 million penalty, later reduced to $14 million — the largest ever imposed on a company in a citizen-led public interest lawsuit to enforce the Clean Air Act.

Exxon did everything it could to battle the ruling. When its appeals failed, the oil giant asked the high court to reconsider whether citizens had standing to sue polluters for environmental harms in the first place.

“At trial, Exxon’s neighbors bravely testified to the harms they suffered from the company’s illegal pollution, painting an ugly picture of what it’s like to live in Exxon’s shadow,” said Josh Kratka, managing attorney at the National Environmental Law Center, one of the plaintiffs’ lead attorneys. “The Supreme Court saw through Exxon’s claim that its neighbors shouldn’t have the right to hold the company accountable for compliance with the Clean Air Act.”

Exxon will now have to pay the fine and make changes to its operations at the facility, where nearby residents continue to live with the consequences of its ongoing pollution.