The Pennsylvania Supreme Court heard arguments on Wednesday on whether a governor can force power plant owners to pay for their greenhouse gas emissions, or whether he first needed approval from the Legislature.

At stake is the Commonwealth’s effort to become the first major fossil fuel state to adopt a carbon pricing policy.

The state’s highest court will make the determination if a lower court was right to halt Pennsylvania’s participation in the Regional Greenhouse Gas Initiative (RGGI) – a multi-state consortium that Gov. Josh Shapiro indicates that he does not support in its current form. RGGI imposes a price and declining cap on carbon dioxide emissions from power plants.

The previous administration under former Gov. Tom Wolf estimated that joining RGGI would reduce the state’s carbon dioxide emissions by 97 million tons to 225 million tons through 2030. That compares to its estimate that Pennsylvania emitted 269 million tons of carbon dioxide equivalents in 2018.

Pennsylvania would be the biggest emissions state in the consortium that includes Connecticut, Delaware, Maine, Maryland, Massachusetts, New Hampshire, New Jersey, New York, Rhode Island, Vermont, and Virginia.

It was estimated by the Natural Resources Defense Council that Pennsylvania would have raised more than $1 billion had it begun participating in RGGI in 2022.

The challenge for Shapiro, in addition to Republican opposition, is that some of the labor unions that backed the former PA Attorney General’s campaign also fought against Wolf’s effort to join RGGI.

The governor has assembled a task force to find a solution. Shapiro’s clean-energy goal is a pledge to ensure Pennsylvania uses 30 percent of its electricity from renewable power sources by 2030 – more than 20 percent greater than the current 8% in state law.