It's not going to get much play in the last month of a presidential race—heck, it may not get much play in Senate confirmation hearings—but the next Supreme Court appointment will likely have a huge impact on the future of environmental law. That's because the Clean Water Act, which has regulated water pollution in the United States since 1972, currently hangs by a slim judicial thread. The main debate is whether the federal government has the authority under the Commerce Clause to regulate all of the nation's waters or only some of them—say, just navigable waters used for commerce, or streams that flow between states. The Supreme Court has examined the Clean Water Act twice during the past seven years, both times skirting the broader question of the law's constitutionality. But recently, in Rapanos v. United States, four justices—Thomas, Roberts, Scalia, and Alito—expressed doubts about whether the Constitution allowed such an expansive interpretation of federal authority over water.

Arguments over the appropriate limits to federal power are, of course, older than the Constitution itself. But ever since FDR's Court-packing threats in 1937, the federal government has been allowed fairly broad power over interstate commerce, from economic regulations to environmental and civil rights laws. If a conservative majority in the Supreme Court started whittling away at this power, environmental laws would likely be the first thing to go. The Endangered Species Act may actually beat the Clean Water Act to the chopping block, given the long-running battle in the lower courts over whether the federal government can regulate species that don't cross state lines or have direct economic value. Chief Justice Roberts took part in this battle while still an appeals-court judge, famously writing that he didn't see how a "hapless toad that, for reasons of its own, lives its entire life in California" had much to do with interstate commerce. Other conservative jurists have been more direct. Fifth Circuit judge Edith Jones wrote, in a dissent to a 2003 decision upholding the Endangered Species Act's protection of cave-dwelling bugs in Texas, that her colleagues had "crafted a constitutionally limitless theory of federal protection" that gave "new meaning to the term reductio ad absurdum."

For now, the reigning judicial philosophy remains one that—in the words of the very decision that earned a dissent from Jones—considers all species, along with most of the country's water, to be part of an "interdependent web" of nature that ultimately has a big impact on both intra- and interstate commerce. It's a judicial philosophy that fits well with the findings of environmental science. Unfortunately, it's also a judicial philosophy that's surviving by a single Supreme Court vote—which, to put the matter in appropriately ecological terms, means it's looking pretty endangered.

--Rob Inglis, High Country News