The Supreme Court Asked the Question Boulder Can’t Answer

T his week, Boulder County’s climate-change suit against Suncor and ExxonMobil finally reached the one court the climate plaintiffs spent a decade avoiding. Taking little interest in the Colorado county’s last-ditch jurisdictional bid to keep running, the Supreme Court justices seem poised to answer the question Boulder didn’t want them to ask. The plaintiffs were right to run, because it is a question they cannot win.

States’ tort laws typically hold a factory financially responsible if it emits toxic fumes that harm its neighbors. Those laws hold the same factory liable if, because of the factory’s fraudulent representations, neighbors don’t take reasonable precautions. Boulder is trying to employ the same laws to hold energy companies financially responsible for the climate-related effects of global emissions — every wildfire, flood, and drought.

Late in oral argument Monday, Justice Amy Coney Barrett put the key question to Boulder’s lawyer, Kevin Russell. Set the Clean Air Act aside, she said, and suppose Colorado passed a statute capping emissions in the other 49 states. Could it? Boulder’s lawyer conceded that it could not. Suppose Colorado’s new law declared that those emissions were harming Coloradans in exactly the ways Boulder alleged. Still no, he agreed. “So,” Barrett asked, how could it be that “the same thing can happen through the tort suit?”

Boulder’s answer tried to downplay the regulatory significance of tort suits like these. Justice Brett Kavanaugh called Russell’s answer “a little cavalier,” which was generous. A Colorado jury that can award billions against companies that produce fuel in Texas and Alberta is regulating Texas and Alberta. Common sense says an individual county cannot accomplish by verdict what its state could not accomplish by statute. It’s no small wonder the plaintiffs spent a decade trying to keep this question away from the justices.

What’s more interesting is why the right constitutional answer to Boulder’s complaint is also the commonsense one, and the reason is instructive about how the Constitution is read.

The energy companies’ basic position is that the Constitution does not permit states to regulate interstate pollution unless Congress says otherwise. Justice Elena Kagan pushed back, asking “Where’s the text for that?” Their lawyers did not point to an article, section, or even a clause of the U.S. Constitution that they said was determinative. They didn’t need to.

The reason one state’s law cannot govern a suit over interstate emissions is that such suits are quarrels between equals. Colorado’s tort law has no special privilege that allows it to apply to global emissions of fuels extracted in Louisiana, refined in Texas, and emitted by a vehicle in Missouri (or any of the other 49 states). As the Supreme Court put it back in 1907, “Each State stands on the same level with all the rest. It can impose its own legislation on no one of the others, and is bound to yield its own views to none.”

That rule was not invented in 1907. The Founders inherited it from the customary law of nations that had been recognized and expounded by jurists like Hugo Grotius and Emmerich de Vattel. The law of nations taught that every sovereign, large or small, is in an important sense the equal of every other and that its laws stop at its borders. When, in 1776, the colonies declared themselves “Free and Independent States,” they acquired the many of the rights nations hold against one another, and when they ratified the Constitution, they surrendered those rights, giving the states instead a federal court to hear their quarrels and a Congress to regulate the commerce among them.

Among the rights the states surrendered was the ability to subject emissions from another state to its own law, even if the effects are felt within its borders. Justice Oliver Wendell Holmes described the bargain: “When the States by their union made the forcible abatement of outside nuisances” — like interstate air pollution — “impossible to each, they did not thereby agree to submit to whatever might be done.” Instead, they agreed that these “outside nuisances” of one state against the other would be governed by federal common law and federal courts. Common law refers to the body of law that has developed over centuries through the case-by-case rulings of judges and juries. While most common law is at the state level, there are enclaves of federal common law.

The Supreme Court made explicit in Illinois v. City of Milwaukee (Milwaukee I) (1972) that federal common law governs cases of interstate pollution. Illinois had asked the Court to hear its complaint that Milwaukee’s sewage was fouling Lake Michigan. The justices sent Illinois to a federal trial court instead, explaining, “When we deal with air and water in their ambient or interstate aspects, there is a federal common law.” The Court’s reasoning was the equal-sovereignty principle in different words. Lake Michigan is bounded by four states, and the pollution of a shared body of water, like the apportionment of a shared river or the fixing of a shared border — or, one might add, the governance of the shared atmosphere — “touches basic interests of federalism” and demands a “uniform rule of decision” no individual state could supply. The Court added a caveat that would soon matter. New federal statutes “may in time pre-empt the field of federal common law of nuisance,” it said, “but until that comes to pass,” federal courts would apply federal common law.

That time came quickly. Nine years later, in Milwaukee II (1981), the Court held that Congress had taken over the job by passing the Clean Water Act. Then, in International Paper Company v. Ouellette (1987) — the precedent the justices spent the most time discussing on Monday — Vermont lakefront owners sued a New York paper mill under Vermont law, pointing to the Clean Water Act’s “saving clause,” a provision declaring that the statute does not extinguish existing rights and remedies. The Court held that the clause saved only New York’s authority over the mill on New York’s shore — a power every state has always had over its own smokestacks and outfalls, which Congress left undisturbed. Finally, in American Electric Power Co., Inc. v. Connecticut (2011), the Court held that the Clean Air Act displaces federal common-law suits over greenhouse gases just as the Clean Water Act had displaced suits over sewage, and that whether any state law suit survives depends on what the Clean Air Act preserves, which is to say, on an analysis like that in Ouellette. Kavanaugh pointed out on Monday that Congress likely enacted and amended the Clean Air Act on the understanding that it was displacing an area governed by federal common law.

These four cases invert the usual rule. Ordinarily, state law applies unless Congress displaces it. For “air and water in their ambient or interstate aspects,” the order runs the other way. State law is out unless Congress lets it in, because the states never had the power to begin with. Kavanaugh told Suncor’s lawyer that the four precedents make it “crystal clear” that Boulder’s theory is a matter for federal law. And, as Chief Justice John Roberts observed, Boulder had emphasized what the energy companies said about the climate, rather than what they contributed to the ambient air, precisely “to evade those decisions.”

The analogy to Ouellette does pose one nuanced issue related to how far federal common law extends and state law retracts. Several justices asked whether a “source state” exists for a suit like this one, so that Boulder could refile under Texas law the way the Vermonters could have sued under New York’s. Suncor’s answer (which makes sense) was that the question has no referent: The defendants are producers rather than emitters, and the emissions come from engines and furnaces everywhere on earth.

Return, then, to Barrett’s hypothetical. The reason Boulder cannot do by jury what Colorado cannot do by statute is that Colorado never had the power either way. It never had the power to legislate emissions limits for the 49 other states, and in 1788, all the states gave up every means of coercing their fellow states by other routes. That answer appears in no clause, but it is no less powerful. It is also the answer the climate plaintiffs have spent a decade avoiding.