HARRISBURG, Pa. (AP) — A Pennsylvania court on Tuesday blocked the centerpiece of Gov. Tom Wolf’s plan to fight climate change, the latest challenge to the Democrat’s effort to make Pennsylvania the first major fossil fuel state to adopt a carbon pricing policy.

Commonwealth Court, in a one-line unsigned order, said it will not allow the official publication of the regulation “pending further order of the court.”

The regulation would require fossil fuel-fired power plants to pay a price for every ton of carbon dioxide they emit starting July 1 in a state that has long been one of the nation’s biggest polluters and power producers.

The regulation was to be published on Saturday. But the court sided with leaders of the Republican-controlled Legislature, who just a day earlier had failed in their final legislative attempt to block the regulation.

Republican lawmakers contend that the regulation is an illegal use of regulatory authority.

Wolf in 2019 ordered his administration to start working on a regulation to bring Pennsylvania into a multi-state consortium of Northeastern and mid-Atlantic states, called the Regional Greenhouse Gas Initiative, which sets a price and declining limits on carbon dioxide emissions from power plants.

The plan has won approval from regulatory bodies and signoff by the governor’s office of general counsel and the attorney general’s office under review for form and legality.