Massachusetts v. EPA (2007)
The Supreme Court ruled 5-4 that the EPA has authority to regulate greenhouse gases under the Clean Air Act. The decision forced the agency to determine whether emissions endanger public health.
The EPA issued its Endangerment Finding in 2009, declaring greenhouse gases a threat to public health and welfare.
The finding became the legal foundation for all federal climate regulations, including the 2024 power plant rules.
The current EPA has repealed the 2009 Endangerment Finding, reversing the legal basis established by Massachusetts v. EPA.
