Supreme Court Chief Justice John Roberts blocked attempts to place a hold on the U.S. Environmental Protection Agency's (EPA) air pollution rules for power plants.

Twenty states, led by Michigan, sought to have SCOTUS stymie enforcement of the Mercury and Air Toxics Standards, which the court found to be illegal in a 5-4 vote last year. SCOTUS ruled that the EPA should have done a cost-benefit anaylsis on the rule prior to writing it, as opposed to doing one during the regulatory process, according to The Hill. 

"Unless this court stays or enjoins further operation of the Mercury and Air Toxics rule, this court's recent decision in Michigan v. EPA will be thwarted," the states argued in a filing to the court late last month. "A stay or injunction is appropriate because this court has already held that the finding on which the rule rests in unlawful and beyond EPA's statutory authority."

Meanwhile, the EPA argued that they were working to address the issue laid out by the court last year, saying it would be handled by next month and that the states would not be adversely affected in the interim. The agency plans to use its cost-benefit analysis in the matter in which the court deemed fit in order to ensure that the 2012 rule meets muster.  

"The requested stay would harm the public interest by undermining reliance interests and the public health and environmental benefits associated with the rule," the EPA wrote in a response brief. "The application lacks merit and should be denied."

Justice Roberts moved on the issue less than 24 hours after the EPA issued its response, opting to toss out the states' request on his own as opposed to bringing it to the full court for consideration and dealing with the possibility of a split 4-4 vote.