In American politics, the Clean Water Act is almost sacrosanct. Despite years of litigation demonstrating the act's defects and significant constitutional questions, it remains virtually unchanged by Congress, primarily because even rational efforts to reform environmental regulations are inevitably painted by their opponents as attempts to poison the environment.

The Supreme Court is not bound by such political constraints. This week, Justice Kennedy filed a concurring opinion joined by Justices Alito and Thomas in Hawkes v. Army Corps of Engineers implying that portions of the CWA might be found unconstitutional, unless Congress adds some much needed clarity to the law. While this is not the first time that a Supreme Court justice has questioned the constitutionality of the CWA — Justice Alito made similar arguments in Sackett v. EPA — it is the first time that three members of the Court have simultaneously expressed willingness to put the CWA on trial. The concurrence is particularly noteworthy because it was drafted by Justice Kennedy — a pivotal swing vote who authored the definitive opinion on the scope of CWA just ten years ago in Rapanos v. United States.

The justices' primary concern is that certain provisions of the CWA might be unconstitutionally vague. Under the CWA, the government has authority to regulate the discharge of dirt or other particulates into the "Waters of the United States." However, the act does not explicitly define WOTUS, leaving government bureaucrats and the courts to interpret the statute's scope.

As one would imagine, the federal government has been exceedingly liberal in interpreting its jurisdiction under the Act — prompting numerous lawsuits. The Court attempted to bring clarity to the meaning of WOTUS in Rapanos v. United States, but the divided opinion in that case has only served to muddy the waters even further.

In Rapanos, the Court was asked to determine whether the CWA applies to property that is adjacent to, but not regularly connected with a traditional waterway. The justices split 4-4-1 on the issue, with Justice Kennedy supplying the swing vote. The four Justices drafting the plurality opinion in that case would have defined WOTUS to include only traditional, "relatively permanent" bodies of water, such as oceans rivers, lakes, and streams and adjacent property with a "continuous surface water connection" to those bodies. The four dissenting Justices would have interpreted the CWA broadly to include virtually any adjacent property. Justice Kennedy's opinion (which has been treated as controlling) attempted to compromise, holding that the CWA applies to property if it bears a "significant nexus" to a traditional navigable waterway.

Ten years and millions of dollars in litigation later, we still don't know what "significant nexus" means. Indeed, that is precisely why the plaintiffs in Hawkes ended up in court to begin with. Violations of the CWA carry significant penalties — both civil and criminal. To avoid these penalties, an individual must know if there were wetlands or other WOTUS on their property before they decide to build. Yet, the significant nexus test is so vague and complicated that it is impossible for a person of ordinary intelligence to predict whether their property falls within CWA regulation.

As a result, the Army Corps of Engineers developed an expensive, time consuming, jurisdictional determination process, whereby property owners can submit the issue to the Corps before they build, so that the government can issue its ruling as to whether there is WOTUS on the property. The plaintiffs in Hawkes spent years in that process.

Therein lies the problem. The Due Process clause requires that ordinary people be able to understand and predict what activities will subject them to criminal penalties. A law that requires hiring private engineers and biologists, plus a years-long administrative process in order to understand what's illegal simply does not meet that standard. It's time Congress did its job and clarified the scope of the CWA. If it doesn't, a growing contingent of Supreme Court Justices seems ready and able to flush the Clean Water Act.

Chance Weldon is an attorney with the Center for the American Future at the Texas Public Policy Foundation.Thinking of submitting an op-ed to the Washington Examiner? Be sure to read our guidelines on submissions.