When the Supreme Court hears arguments October 5^th in Suncor Energy v. County Commissioners of Boulder, the oil companies will argue that municipalities cannot pursue state-law claims for damages caused by the marketing of fossil fuels. Boulder seeks to prove that it has suffered damages from the defendant companies’ contribution to extreme heat, storms, wildfires, and other harmful effects of climate change. The oil companies, backed by the Department of Justice (DOJ) as amicus curiae, contend Boulder’s claims for compensation are preempted by, among other things, the Clean Air Act.

Boulder has solid rebuttals to all of its opponents’ preemption arguments. This post deals only with their Clean Air Act theory. It shows how recent actions of the Environmental Protection Agency (EPA) disclaiming any statutory authority to regulate climate-changing pollution have radically undermined that theory.

Relying on Supreme Court precedent in climate change cases, DOJ’s Suncor brief argues that the Clean Air Act gives EPA statutory authority to regulate greenhouse gas pollution at the federal level. Right so far. But the brief goes on to infer, wrongly, that EPA’s Clean Air Act authority to regulate those emissions preempts Boulder’s state-law claims for damages.

DOJ’s preemption theory is rickety enough on the correct understanding that EPA has statutory authority to regulate. But EPA has just thrown DOJ a big curve ball.

Last week EPA proposed to find that it has no authority under Section 111 of the Clean Air Act to regulate climate-changing emissions from power plants. That proposal comes atop a final EPA rule issued in February taking the same position under Section 202 of the Act regarding motor vehicles’ climate pollution. See 91 Fed. Reg. 59002 (Sept. 17, 2026); 91 Fed. Reg. 7686 (Feb. 18, 2026).

A broad coalition of states, public health and environmental groups, and industries is challenging EPA’s February action in the D.C. Circuit and will do the same in comments on last week’s proposal. But taking EPA’s current position at face value, if the Clean Air Act gives EPA no such regulatory authority, then DOJ’s already shaky statutory preemption theory in Suncor collapses entirely.

Let’s walk through the government’s statutory preemption theory first on DOJ’s premise that EPA does have Clean Air Act authority to regulate climate-changing emissions, and then consider the impact of EPA’s reversal of position.

DOJ’s brief in Suncor starts from the holding of American Electric Power v. Connecticut, 564 U.S. 410 (2011), that EPA does have authority to curb power plants’ climate pollutants, and this displaces federal common law claims for emissions abatement even if EPA has not exercised that authority. American Electric Power expressly declined to rule on whether that statutory authority preempts state-law claims. That is what the DOJ Suncor brief now argues for.

DOJ’s brief could not entirely avoid the inconvenient fact that EPA had already disclaimed its Clean Air Act authority to regulate climate pollutants from motor vehicles last February. The brief buried this point in a footnote on the last page. It asserts: “But that conclusion about Section [202] does not apply to EPA’s authority under Section [111] to regulate emissions from stationary sources.” Now EPA has knocked the legs out from that footnote, and DOJ’s straddle between vehicles and power plants has become impossible.

This is not the place to explain why the courts will likely reject both EPA actions; you can find good summaries here, here, and here, and in detailed submissions to EPA here and here.

But EPA’s comeuppance will not come before the Supreme Court considers the Suncor case next month. As in Puerto Rico Dept. of Consumer Affairs v. Isla Petroleum Corp., 485 U.S. 495, 504 (1988), EPA’s disclaimer of authority cannot “leave behind a pre-emptive grin without a statutory cat.”

To be clear, Boulder has strong arguments against preemption even if the Court ignores EPA’s disclaimer. Boulder emphasizes that it is seeking damages, not emissions abatement. Monetary compensation is something the Clean Air Act simply does not address, let alone preclude.

In very similar circumstances under the Clean Water Act, the Supreme Court held that “nothing in the Act bars aggrieved individuals from bringing a nuisance claim pursuant to the law of the source State.” International Paper Co. v. Ouellette, 479 U.S. 481, 497 (1987). Boulder argues that the source-state-law proviso should not apply to cases seeking monetary damages, as opposed to emissions reduction. But even if Ouellette’s source-state rule applies here, that case contradicts DOJ’s statutory argument for total preemption.

The oil companies try to flip the script by claiming suits like Boulder’s are barred unless the Clean Air Act affirmatively authorizes them. Neither Ouellette nor any other Supreme Court case supports that novel proposition.

In conclusion, EPA has made the oil companies’ task on October 5^th significantly more difficult. It will be a very interesting argument.