The rulings don’t uphold the methane and mercury rules but rather allow the administration to enforce it while underlying legal challenges continue – a process that could take years.
Separately, the court is considering another series of emergency appeals requiring coal and new natural gas power plants to dramatically cut emissions.
Republican officials in two dozen states had asked the Supreme Court to halt the methane rule, arguing that the Environmental Protection Agency was acting outside of its authority to approve it.
The agency estimates the rule will slash methane emissions from oil and gas operations by nearly 80% through 2038.
An appeals court in Washington, DC, previously denied the states’ request to put the new methane regulations on hold.
Methane, the main component of natural gas and a byproduct of fossil fuel drilling, is a powerful source of climate pollution with more than 80 times the warming power of carbon dioxide during its first two decades in the atmosphere.
The mercury rule, which took effect in July, requires certain coal-fired plants to reduce both mercury emissions and also tightens emission standards for other metals, such as arsenic and chromium. Republican officials in 23 states, including North Dakota, West Virginia and Alaska, along with several industry groups, sued to block the rule.
In a filing to the Supreme Court, the states argued that the agency could not “quantify any relevant or meaningful public health or environmental benefit from the mandated reduction.” Industry groups warned that the costs to update plants would be “substantial” and predicted that prices for electricity would increase.