The U.S. Supreme Court today declined to hear a 2015 lawsuit filed by oil industry leaders, which challenged Oregon's authority to enforce the Clean Fuel Standard, a policy aimed at decreasing transportation emissions.

The Clean Fuel Standard was passed by the Oregon Legislature in 2015 and went into effect 2016. It requires out-of-state oil companies to reduce the amount of carbon pollution they emit via diesel and gasoline by 10 percent in 10 years—beginning in 2016.

The policy has already helped reduce transportation fuel pollution by over 2.73 million tons, Oregon Environmental Council said in a statement. That's the equivalent of removing 580,000 cars from the road for a year.

The lawsuit filed four years ago by the American Fuels and Petrochemical Manufacturers, the American Trucking Association and Consumer Energy Alliance argued that the legislation gave Oregon unconstitutional authority to regulate out-of-state commerce.

In September, the Ninth Circuit Court of Appeals issued an opinion dismissing the case. Today, Justices on the U.S. Supreme Court tossed the suit.

Local environmental advocacy groups Earthjustice, Oregon Environmental Council and Climate Solutions intervened on behalf of the Clean Fuel Standard in court.

"Big Oil's last ditch effort to undercut state authority to require cleaner fuels has failed again," Amanda Goodin, an attorney with Earthjustice, said in a statement. "This will help pave the way for more states to adopt programs to reduce their greenhouse gas emissions with confidence that their efforts will be upheld in court."