The environmental lawsuits active in federal courts this week center on one dominant fight — a cluster of petitions in the D.C. Circuit challenging the EPA’s repeal of the 2009 greenhouse gas endangerment finding — alongside several other high-stakes cases moving in parallel: the NAACP’s Clean Air Act suit against Elon Musk’s xAI in Mississippi, a Supreme Court climate preemption case out of Boulder County, two recent Supreme Court rulings on oil and pipeline jurisdiction, an Eleventh Circuit appeal over Florida manatees, and a novel California union challenge to a return-to-office order under the state’s environmental review law.
The EPA Endangerment Finding Repeal: The Headline Fight
On February 12, 2026, the EPA signed a final rule rescinding the 2009 endangerment finding and eliminating every federal greenhouse gas standard that depended on it, including all vehicle emission rules for light-, medium-, and heavy-duty vehicles. The rule was published in the Federal Register on February 18, 2026, and the lawsuits started landing the same day.1U.S. Environmental Protection Agency. Final Rule: Rescission of Greenhouse Gas Endangerment
Who Sued, and When
A coalition of seventeen health and environmental groups filed first, on February 18, 2026, represented by Earthjustice and the Clean Air Task Force. The plaintiffs include the American Public Health Association, the American Lung Association, the Sierra Club, the Natural Resources Defense Council, the Environmental Defense Fund, the Center for Biological Diversity, and the Union of Concerned Scientists.2Earthjustice. Earthjustice and Partners Sue EPA for Illegal Repeal of Climate Protections Their core argument is that the EPA is relitigating positions the Supreme Court already rejected in Massachusetts v. EPA and ignoring a statutory duty to regulate pollutants that endanger public health.3NRDC. NRDC Coalition Sues Over Endangerment Rollback
Two days later, on February 20, 2026, the Zero Emission Transportation Association — an electric vehicle industry group — filed its own petition targeting both the rescission and the elimination of vehicle standards.4Sabin Center for Climate Change Law. Zero Emission Transportation Association v. EPA
On March 12, 2026, Democracy Forward filed on behalf of the Service Employees International Union, which represents two million health care, public service, and property service workers. SEIU argues its members are disproportionately exposed to climate-driven hurricanes, floods, wildfires, and extreme heat.5Democracy Forward. Workers Sue to Stop Trump-Vance Administration’s Plan to Gut EPA’s Climate Protections
On March 19, 2026, a coalition led by the attorneys general of Massachusetts, California, New York, and Connecticut filed a separate petition for review. The coalition totals 24 states, the District of Columbia, the U.S. Virgin Islands, the Governor of Pennsylvania, and roughly a dozen cities and counties, including New York City, Los Angeles, Chicago, Boston, San Francisco, Denver, Cleveland, Columbus, and Harris County, Texas.6New York Attorney General. Massachusetts et al. v. EPA Petition for Review They argue the rescission violates both the Clean Air Act and the Administrative Procedure Act and contradicts Supreme Court precedent.7California Attorney General. President Trump Ignores Climate Science, Law Will Hold Him Accountable
Most recently, on May 20, 2026, youth petitioners in Venner v. EPA moved for an emergency stay of the rescission while litigation proceeds, invoking the Religious Freedom Restoration Act and the Fifth Amendment and arguing the rule would cause irreversible increases in carbon emissions. Other petitioners in the consolidated cases have not taken a position on that motion.8Sabin Center for Climate Change Law. American Public Health Association v. EPA Case Collection
What’s Actually at Stake
The rescission eliminates all federal greenhouse gas emission standards for light-, medium-, and heavy-duty vehicles and engines. Manufacturers no longer have obligations to measure, control, or report vehicle greenhouse gas emissions for any model year, including vehicles already built.1U.S. Environmental Protection Agency. Final Rule: Rescission of Greenhouse Gas Endangerment The finding also underpinned power plant greenhouse gas standards and rules covering buildings and industrial operations, and the EPA has separately proposed repealing the power plant standards, with the final version expected at the Office of Management and Budget in early spring 2026.9U.S. Environmental Protection Agency. Greenhouse Gas Standards and Guidelines for Fossil Fuel-Fired Power Plants
One wrinkle worth flagging: removing the federal regulatory framework may actually expose energy companies to more state-court lawsuits, not fewer, because the preemption defenses they have relied on in climate tort cases become harder to maintain without an active federal scheme.10World Resources Institute. Endangerment Finding Repeal Explained
The Legal Argument
The EPA grounded its repeal in a reinterpretation of the Clean Air Act rather than a direct attack on climate science. The agency argues Section 202(a) was never meant to cover global climate change, invoking West Virginia v. EPA (2022) and Loper Bright Enterprises v. Raimondo (2024) to argue that regulating greenhouse gases is a “major question” requiring explicit congressional authorization.11Salata Institute, Harvard University. The Legal Reasoning Behind the Endangerment Rescission It also claims eliminating U.S. vehicle emissions would have “no material impact on global climate indicators through 2100.”12U.S. Environmental Protection Agency. President Trump and Administrator Zeldin Deliver Single Largest Deregulatory Action in U.S. History
Challengers point to Massachusetts v. EPA (2007), where the Court found the Clean Air Act’s definition of “air pollutant” “sweeping” and “capacious” enough to cover greenhouse gases and directed the EPA to use scientific judgment in endangerment determinations.13Columbia Law School, Sabin Center. Massachusetts v. EPA They argue West Virginia and Loper Bright dealt with different Clean Air Act sections and different regulatory tools, and that neither overruled Massachusetts. In Utility Air Regulatory Group v. EPA (2014), the Court distinguished Massachusetts by calling the addition of greenhouse gas standards for new motor vehicles a “modest step” consistent with congressional intent.14Harvard Environmental and Energy Law Program. Eliminating the Foundation: Vulnerabilities in EPA’s Endangerment Finding Rescission
As of mid-2026, the D.C. Circuit cases are in early stages. Merits briefing is pending, and legal observers expect the litigation to take years and likely reach the Supreme Court.15Spotlight PA. EPA Lawsuit: Greenhouse Gas Trump Rollback
NAACP v. xAI: Unpermitted Turbines in Mississippi
In April 2026, the NAACP sued Elon Musk’s artificial intelligence company xAI and its subsidiary MZX Tech in the U.S. District Court for the Northern District of Mississippi, represented by Earthjustice and the Southern Environmental Law Center. The suit alleges that xAI is operating dozens of unpermitted gas turbines at a power plant serving the “Colossus 2” data center in Southaven, Mississippi, in violation of the Clean Air Act. The turbines started at 27 and have grown to at least 33, with the potential to emit over 1,700 tons of nitrogen oxides, 500 tons of carbon monoxide, 180 tons of fine particulate matter, and 19 tons of formaldehyde annually.16Earthjustice. xAI Illegal Gas Power Plant Data Center Colossus
On May 6, 2026, plaintiffs filed for a preliminary injunction to halt the turbines, citing imminent health harms to nearby communities.17Earthjustice. NAACP Asks Court for Emergency Action to Stop Illegal Air Pollution From xAI’s Data Center Power Plant A week later, the Department of Justice signaled it may intervene, citing the federal government’s “substantial interest” in Clean Air Act interpretation and the promotion of “America’s global AI dominance.”18Utility Dive. DOJ May Intervene in NAACP Lawsuit Over xAI’s Data Center Gas Turbines
Suncor v. Boulder County at the Supreme Court
The Supreme Court granted certiorari on February 23, 2026, in Suncor Energy v. Board of County Commissioners of Boulder County. The case asks whether federal law preempts state-law claims seeking damages for injuries caused by greenhouse gas emissions. The Colorado Supreme Court ruled in May 2025 that federal law did not preempt the state claims, and Suncor sought review. The Court added a threshold question about whether it has jurisdiction to hear the case at this procedural stage, which could lead to dismissal before the merits.19SCOTUSblog. Suncor Energy Inc. v. County Commissioners of Boulder County Petitioners filed their merits brief on May 14, 2026, and respondents’ brief is due July 27, 2026. No oral argument date has been set.20Supreme Court of the United States. Docket: Suncor Energy v. Boulder County, No. 25-170
Chevron v. Plaquemines Parish: Louisiana Coastal Damage
On April 17, 2026, the Supreme Court ruled 8-0 in Chevron USA Inc. v. Plaquemines Parish that Chevron could move a $745 million state-court lawsuit over Louisiana wetlands damage to federal court. Justice Thomas wrote that because Chevron’s wartime crude oil production was “closely connected” to its federal contract to refine aviation gasoline for the military, the case “relates to” the company’s performance of federal duties under the federal officer removal statute.21Supreme Court of the United States. Chevron USA Inc. v. Plaquemines Parish, No. 24-813 The ruling applies to 11 of the 42 coastal damage lawsuits that Louisiana local and state officials have filed against oil and gas companies. It did not address the underlying merits.22Louisiana Illuminator. Supreme Court Chevron Ruling
Enbridge v. Nessel: Line 5 Stays in Michigan Court
Also in April 2026, the Supreme Court unanimously ruled in Enbridge Energy v. Nessel that Enbridge’s attempt to remove Michigan Attorney General Dana Nessel’s Line 5 pipeline lawsuit to federal court failed because the company missed the 30-day statutory removal deadline by 887 days. Justice Sotomayor wrote that the deadline is not subject to equitable tolling.23Supreme Court of the United States. Enbridge Energy, LP v. Nessel, No. 24-783 The state’s case against the 645-mile pipeline stays in Michigan state court. A separate December 2025 federal district court ruling held that Michigan’s attempt to revoke Enbridge’s easement in the Straits of Mackinac was preempted by federal law, and Governor Whitmer has appealed.24Michigan Advance. U.S. Supreme Court Unanimously Backs Nessel, Keeps Line 5 Case in Michigan Court
Bear Warriors United v. Lambert: Florida Manatees
In Florida, Bear Warriors United v. Lambert is testing the Endangered Species Act’s citizen enforcement provisions at the Eleventh Circuit. An environmental group sued the Florida Department of Environmental Protection, alleging the state’s lax regulation of septic tanks and wastewater discharges into the Indian River Lagoon destroyed seagrass habitat and caused endangered manatees to starve. The district court granted summary judgment for the plaintiffs on causation and in May 2025 issued a permanent injunction ordering the state to apply for an incidental take permit, establish a manatee feeding program, and stop issuing new septic tank permits in the affected watershed. Florida appealed, arguing the ruling amounts to unconstitutional federal commandeering of state regulatory authority. The Eleventh Circuit heard oral arguments in late April 2026, and the injunction remains in effect after the appeals court denied a stay.25Appellees’ Brief, Bear Warriors United v. Lambert, Nos. 25-11612 and 25-11821
California CEQA Challenge to Return-to-Office
In a novel use of environmental law, the California Attorneys, Administrative Law Judges and Hearing Officers in State Employment (CASE) is challenging Governor Gavin Newsom’s mandate requiring state employees to return to the office four days a week, effective July 1, 2026. The union argues the mandate is a “project” under the California Environmental Quality Act and would force over 90,000 employees to commute, generating an estimated 15,000 tons of additional carbon dioxide emissions per month.26The Sacramento Bee. California State Workers Challenge Return-to-Office Mandate As of late May 2026, the union has sent pre-litigation letters to more than 100 state departments but has not yet filed suit.27Los Angeles Times. Union Challenges Return to Office With California’s Landmark Environmental Law
Why the Docket Is This Full
Federal environmental enforcement has fallen sharply. During the first year of the current administration, the Department of Justice filed just 21 environmental enforcement cases and collected $15.1 million in penalties, compared to $1.88 billion in enforcement penalties in 2024. Earthjustice alone opened 632 legal matters during that same first year, a 53% increase from the 414 matters it opened in the same period of Trump’s first term. That gap helps explain why environmental organizations, state attorneys general, and labor unions have moved so aggressively through private litigation and state-level action. Colorado adopted its first rule to curb landfill air pollution in December 2025, and a New Jersey court upheld rules under that state’s Environmental Justice Law in January 2026, though industry has appealed to the state Supreme Court.28Earthjustice. Counter-Act Spring 2026