President Joe Biden's administration took a massive hit on the environmental front thanks to a 5--4 decision at the hands of the U.S. Supreme Court.

According to NBC News, the high court ruled in blocking the Environmental Protection Agency's (EPA) interstate air pollution regulation.

The ruling came as a victory for three Republican states who led the charge against the EPA, which included Indiana, Ohio and West Virginia.

It should be noted that the high court's decision is provisional right now, meaning more litigation will likely decide the final outcome. But it's a step in the right direction.

What's going on?

The decision was both widely celebrated and frowned upon, with several environmental groups expressing their concerns that eliminating the rule will harm the environment, animals and humans.

"Today’s decision is deeply disappointing. It will result almost immediately in pollution that endangers the health of millions of people," the Sierra Club and the Environmental Defense Fund wrote in a joint statement.

Justice Neil Gorsuch wrote the majority opinion in the ruling.

NBC News noted:

In the majority opinion, Justice Neil Gorsuch wrote that the EPA's decision to implement the rule even though it was partially blocked was part of the problem, as the agency did not address how effective the regulation would be if it were only partly in effect.

The government failed to show "whether the cost-effectiveness analysis it performed collectively for 23 states would yield the same results and command the same emission-control measures if conduct for, say, just one state," Gorsuch wrote.

Notably, Justice Amy Coney Barrett, a conservative, sided with the high court's three liberal justices in dissenting.

NBC added:

She wrote that the court had blocked a major air pollution rule "based on an undeveloped theory that is unlikely to succeed on the merits" when the legal question is finally adjudicated.

What is it?

The EPA's "good neighbor" plan would apply to 23 "upwind" states whose emissions can affect pollution levels in surrounding "downwind" states.

At the time, the EPA claimed the plan would "help prevent premature deaths, reduce emergency room visits and cut asthma symptoms by limiting the amount of smog."

States are already required to be "good neighbors" under the Clean Air Act.

The EPA has lost two previous cases at the hands of the Supreme Court.