SAN FRANCISCO – Last month the United States Supreme Court issued a 5-4 decision on a pair of cases involving the authority of the federal government to regulate wetlands. Some see the decision as an assault on the Clean Water Act but others regard it as a necessary check on expanding federal reach.

In the June 19 split decision on Rapanos v. United States and Carabell v. U.S. Army Corps of Engineers, four justices voted in favor of a broad interpretation of the U.S. Army Corps of Engineers’ regulatory jurisdiction over wetland areas. Five justices explained a need to rein in the extent to which the Corps could assert its regulatory authority, but provided little additional guidance to the Corps as to what should constitute a regulated wetland.

Wetlands themselves provide numerous valuable “ecosystem services.” They can act like sponges to mitigate and store flood flows, filter sediments and pollutants which might otherwise impair downstream waters, and provide habitat for a number of species. But not all wetlands are of equal value.

Some wetland areas, hydrologically far removed from larger bodies of water, have a minimal effect on downstream waters. Others are small enough that their impact on larger bodies of water downstream is negligible. One might argue that the Corps should be able to regulate all of these waters but allow development on wetlands determined to be minimally influential.

As Justice Scalia noted in his majority opinion, “the average applicant for an individual permit spends 788 days and $271,596 in completing the process.” The excessive expense and lost time in the evaluation, and sometimes litigation over every patch of mucky ground, is far from a trivial concern.

The minority opinion, from Justices Stevens, Souter, Ginsberg and Breyer, contended that the governments’ regulatory authority extended to “all identifiable tributaries that ultimately drain into large bodies of water.” This would have far overreached reasonable regulation.

Using the test of whether a particular area ultimately drains into a large body of water leaves virtually all waterways, no matter how inconsequential, to government regulation. Theoretically, any runoff or subsurface flow could ultimately contribute to water pollution. Runoff may include ephemeral waterways on isolated slopes to rivulets from lawn irrigation systems. Subjecting all of it to permit-style regulation would result in excessive paperwork and bureaucratic overhead, with little real chance of maintaining or improving the nations’ water quality.

The issue, then, is what level of regulation is reasonable, in order to maintain water quality, while protecting individuals from needless and invasive regulation. The court did not address this issue directly.

In the majority opinion, Justice Scalia, on behalf of Justices Thomas, Alito, and Roberts, said that the test should be whether or not there is a continuous surface connection between a wetland and a navigable body. In the tie-breaking vote, Justice Kennedy stated that the determining factor should be whether or not there is a “significant nexus” between the wetland in question and a navigable waterway. Neither definition truly provides a clear distinction between wetlands that the federal government could regulate and ones they could not.

Determination of a continuous surface connection is sometimes tricky to quantify and does not necessarily address the extent to which wetlands provide safeguards through subsurface pathways or ephemeral and indirect surface flows. Determination of a “significant nexus” is no easy task because of the multiple pathways and impacts of a wetland within a given hydrologic system.

This is why some claim that the justices’ decision did not go far enough, because it left the question of wetland jurisdiction to be determined on a case-by-case basis. It is the role of the court to interpret the law, but not to rewrite it when the original law is ambiguous, as in this case.

The Clean Water Act does not clearly spell out which waters should be subject to government regulation, essentially leaving it to the Corps of Engineers to determine their own guidelines. The lack of clear definitions on this matter means that wetlands have increasingly been subject to jurisdictional “creep,” with the tendency to expand the federal reach beyond the original intent. Though some see such expansion as crucial to the safety and quality of the nation’s water systems, the high court appears to understand that excessive regulation does not automatically translate to environmental improvement.

In the short term, the Supreme Court’s mandate for a case-by-case evaluation will cause additional expense on the part of both the federal government and those entities wishing to develop or modify areas potentially classified as wetlands. In the long term, however, the ruling should encourage lawmakers and regulators to come up with a clear classification scheme less prone to overreaching misinterpretation.