A coalition of states and cities has filed suit against the U.S. Environmental Protection Agency after the agency, under the Trump administration, eliminated the rule that limited greenhouse gas emissions from power plants.

The litigation marks the first major courtroom test of the administration's deregulation agenda for the electricity sector. At stake is the regulatory framework that determines how coal- and gas-fired generators account for their emissions — and what, if anything, replaces it.

Who is suing, and over what?

The plaintiffs are state governments and city governments that had previously defended the emissions rule in court. Their core argument: the EPA cannot simply repeal limits on power plant carbon output without providing a lawful replacement, because the agency retains a statutory duty under the Clean Air Act to regulate carbon dioxide from existing sources.

By eliminating the rule outright, the EPA leaves the second-largest source of U.S. greenhouse gas emissions — the power sector — without federal carbon constraints, a outcome the suing states argue is unlawful.

What does the repeal change?

The eliminated rule had required emissions reductions from fossil-fuel power plants. Its removal relieves plant operators of compliance planning tied to that framework.

For utilities, the immediate practical effect is regulatory uncertainty rather than clarity. Grid operators and investors have repeatedly flagged that legal challenges to emissions rules complicate decisions on plant retirements, fuel switching and new capacity — regardless of which side prevails.

State regulators in the suing jurisdictions argue the rollback also undermines their own planning. Several states have binding clean electricity targets and rely on a federal floor to prevent emissions leakage from imported power.

What happens next?

The case now moves through the federal courts, where the timetable and venue will shape how long the sector operates without a federal power plant carbon rule. The litigation follows a pattern set in prior regulatory cycles, when repeal-and-replace efforts by successive administrations each drew multistate legal challenges.

The decisive milestone is the first substantive court ruling on whether the EPA's repeal satisfies its obligations under the Clean Air Act. That decision will determine whether the power sector faces a restored emissions rule, a rewritten one, or an extended period with no federal carbon limits on existing plants.