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On Tuesday, the Supreme Court substantially weakened federal limitations on raw sewage discharge into nearby bodies of water. Its 5–4 decision will, in practice, free cities to dump substantially more sewage into rivers, lakes, oceans, and bays, degrading water quality standards around the country. The majority achieved the goal by rewriting a key provision of the Clean Water Act that has, for decades, protected Americans against dangerous pollution. With that guardrail gutted, the majority effectively greenlit the mass release of human waste into the nation’s water supply. As Justice Amy Coney Barrett explained in dissent, the court “offers nothing to substantiate” its “puzzling” conclusion—nothing, that is, besides evident sympathy for polluters and callous apathy toward those who will suffer from its decision.

Tuesday’s ruling in San Francisco v. EPA revolves around restrictions on the release of pollution into large bodies of water. Like many American cities, San Francisco’s wastewater treatment system combines sewage and stormwater, processing both simultaneously. Heavy precipitation, however, can overwhelm the system’s capacities, forcing the city to release untreated water into the Pacific Ocean and the San Francisco Bay. The Clean Water Act directs the Environmental Protection Agency to regulate this discharge to ensure that it does not pose a threat to human health or ecosystems. Specifically, the EPA may issue permits that set “effluent limitations” as well as “any more stringent limitation” necessary to protect the proper “water quality standard.”

This conflict arose because San Francisco dumps a ton of waste into the bay and ocean, and the federal government told it to stop. Justice Samuel Alito’s majority opinion ignored the consequences of the city’s continual sewage discharge, leaving Barrett to point out that this practice has led to “discoloration, scum, and floating material, including toilet paper” in its waters. To avoid complying with the EPA’s mandate, San Francisco launched a frontal assault on the Clean Water Act. It argued that the law only allows the EPA to set explicit, numerical limits on the amount of waste that the city discharges. Under this theory, the agency could not impose other, more targeted restrictions. It could not, for instance, compel the use of “pollution-treatment technologies” that reduce the harmful impact of the discharge itself. Nor could it order the city to stop discharging waste in specific, highly sensitive areas where it poses a heightened risk to the environment.

The full court rejected this sweeping argument, noting that it has no basis in the text of the statute. But Alito, joined by the four other male justices, then went on to side with San Francisco anyway, over a dissent from Barrett and the three liberals. The majority deployed a different theory that, Barrett noted, was “largely of its own making,” essentially improvising an excuse to hinder the EPA. It held, bizarrely, that the EPA may not ensure a city’s compliance with federal law by testing nearby waters to ensure that they meet the necessary standards. In other words, the majority held that the existence of clean water is not required by the Clean Water Act. As long as cities try to keep their water safe, they can get away with maintaining objectively unsafe water supplies.

How does the majority reach this upside-down conclusion? With a sleight of hand so clumsy that it would fail to impress a kindergarten class. The Clean Water Act, Alito wrote for the court, authorizes the EPA to place any “limitation” on sewage discharge. But, according to the dictionary, a “limitation” is a “restriction or restraint imposed from without ”—that is, a specific direction on how to limit wastewater imposed by the EPA. By demanding that water meet certain, measurable quality standards, the EPA mandates “a particular end result” without saying exactly how it “must be achieved”—that is, the EPA is placing the onus on San Francisco to “figure out what it should do” and impose a restraint on itself. The “direct source” of this restriction therefore “comes from within,” not “from without,” and thus cannot qualify as a “limitation.”

This argument does not even round up to logic. It is, as Barrett put it in dissent, “wrong as a matter of ordinary English,” and utterly “contrary to the text” of the statute itself. “The entire function” of the law “is to ensure that permitted discharges do not violate” acceptable water quality standards, she wrote. “Why would that broad authority not allow EPA” to tell cities that “they must not cause or contribute to a violation” of those standards? Surely, this instruction qualifies as a “limitation.” After all, “it is commonplace” for “limitations” to state “that a particular end result must be achieved” without specifying precisely how it must be achieved. For instance, “a doctor could impose a ‘limitation’ on a patient’s diet by telling the patient that she must lose 20 pounds over the next six months, even if the doctor does not prescribe a specific diet and exercise regimen. And an airline could impose a ‘limitation’ on the weight of checked bags, even though it does not tell passengers what items to pack.”

Alito protested that this definition of “limitation”—the one used by a regular speaker of English—conflicts with the legislative history of the Clean Water Act as well as its “broader statutory scheme.” These claims do not withstand Barrett’s withering rebuttal. Alito purported to show that Congress revised the law in 1972 to eliminate a “backward-looking approach” to water maintenance, absolving cities of responsibility as long as they tried to improve their water supplies. As Barrett persuasively demonstrated, though, Congress had no such intention. Rather, it sought to “supplement rather than replace” standards based on water quality, empowering the EPA to compel detailed restrictions on discharge while still requiring a water supply that is measurably safe to humans. “There is no getting around it,” Barrett wrote: The Clean Water Act does not merely encourage cities to discharge less waste; it also demands water that is, in fact, clean.

Of course, Barrett’s commonsense position lost out by one vote. And so, as of Tuesday, this federal guarantee of actually clean water, enshrined by Congress and enforced for half a century, is no more. Under a Democratic president, the EPA might try to make up the difference by imposing extra-vigorous restrictions on the quantity of sewage that cities can dump into waterways. Under Donald Trump, the agency will likely take the decision as permission to abandon meaningful enforcement of the Clean Water Act.

Curiously, San Francisco v. EPA marks the second time that the court has divided along gender lines in an environmental dispute, following last term’s Ohio v. EPA . In both cases, Justice Amy Coney Barrett wrote the dissenting opinion. In both, she sounded disappointed that the majority would warp the law beyond recognition to let polluters off the hook. The justice should not be mistaken for a conservationist; her frustration with her male colleagues seems rooted in incredulity that they would contort a statute so brazenly to further kneecap the EPA. In these cases, Barrett is at least trying to act like a real judge. But with a 6–3 conservative supermajority, her flashes of integrity are not enough to protect us from the majority’s contempt for a livable environment.