As noted, the Supreme Court decided the much anticipated consolidated Commerce Clause-flavored challenges to the Clean Water Act, Rapanos v. United States and Carabell v. United States, trimming back the scope of federal wetlands regulation. (Cato filed an amicus brief in support of the petitioners in Rapanos, which you can access here.) The decision is a mixture of equal parts good news and not-quite-so-good news.

The good news is Justice Scalia’s opinion for the court, joined by three other justices: the Chief, Justice Thomas, and Justice Alito. The not-quite-so-good news is the concurrence, written by Justice Kennedy–the all important fifth vote–which significantly qualifies Justice Scalia’s plurality decision, and the concurrence written by Chief Justice Roberts.

First, a bit of background.

The Clean Water Act, among other things, regulates point source pollution (pollution discharged through a drain of some sort). The Act says regulators can impose criminal sanctions for any pollution into “navigable waters,” defined as “waters of the United States.” But one bit of the Act, imposing reporting requirements and such on state dredging programs, refers to federal waters “adjacent to” navigable water. Federal environmental regulators suggest, based on this apperance of the word “adjacent,” that the Act covers some non-navigable waters.

Indeed, federal regulators go much, much further than that. They argue that any land with a “hydrological connection” to navigable water is within federal regulatory authority. That means even a trickle of surface water or ground water that might eventually wend its way off a land-locked piece of property, trickling drops into a navigable body of water scores of miles away, or more, is within federal power. Hence, the prosecution of John Rapanos: A Michigan commercial developer, Mr. Rapanos dumped sand on one parcel of land in preparation for a real estate development. He was slapped with criminal charges–and threatened with jail time–because grains of that sand may be carried by rainwater through on old run-off drain and, after an epic journey through culverts, creeks and ditches, end up in the Kawkawlin River, twenty miles or so away.

Needless to say, this reading of the Clean Water Act stretches its text past the breaking point. Says Scalia’s opinion:

The extensive federal jurisdiction urged by the Government would authorize the Corps to function as a de facto regulator of immense stretches of intrastate land-an authority the agency has shown its willingness to exercise with the scope of discretion that would befit a local zoning board. We ordinarily expect a “clear and manifest” statement from Congress to authorize an unprecedented intrusion into traditional state authority. The phrase “the waters of the United States” hardly qualifies.

Likewise, the Corps’ interpretation stretches the outer limits of Congress’s commerce power and raises difficult questions about the ultimate scope of that power. Even if the term “the waters of the United States” were ambiguous as applied to channels that sometimes host ephemeral flows of water (which it is not), we would expect a clearer statement from Congress to authorize an agency theory of jurisdiction that presses the envelope of constitutional validity.

In sum, on its only plausible interpretation, the phrase “the waters of the United States” includes only those relatively permanent, standing or continuously flowing bodies of water “forming geographic features” that are described in ordinary parlance as “streams[,] … oceans, rivers, [and] lakes.” The phrase does not include channels through which water flows intermittently or ephemerally, or channels that periodically provide drainage for rainfall.

Read by itself, the upshot of Scalia’s opinion is a significant victory for federalism. It rejects environmental regulators’ “hydrological connection” test for federal jurisdiction over wetlands and, furthermore, requires that regulated wetlands have a continuous, standing surface connection to navigable water. It recognizes, moreover, that the Clean Water Act is at the periphery of federal commerce power.

Unfortunately, the Chief Justice’s and Justice Kennedy’s concurring opinions muddy the water (bad puns not intended).

First Kennedy. Kennedy says the Clean Water Act doesn’t raise difficult questions of federal commerce power. Instead, based on a simple interpretation of the Act’s text and legislative purpose, he contends only that regulators lack control over any water–surface or ground, continually running or intermittent–without a “significant nexus” to navigable water. What this means exactly we don’t know. Kennedy wants the lower courts to come up with a significant nexus text–one more bite at the apple, in other words.

Chief Justice Roberts, moreover, invites the EPA to engage in formal notice and comment rulemaking (that’s legalese for a regulatory proceeding that announces a new rule after public input) about the scope of federal power over wetlands and suggests that if it engages in such rulemaking, it would deserve great leeway in the lines it draws. This is a very significant qualification, as it suggests he would be less inclined to second-guess the agency in such a case, even if it draws lines around federal authority that are different than the Court’s preferred lines. Roberts’ concurrence deepens my suspicion that he is more committed to a broad theory of agency discretion than any other justice on the Court, including Scalia.