In 1972 Congress passed the Clean Water Act to protect the “waters of the United States” by empowering the Environmental Protection Agency (EPA) “to restore and maintain the chemical, physical, and biological integrity of the Nation’s waters.” At first glance, this seems like a sensible, even commendable, piece of legislation. After all, who doesn’t want clean water?

But there’s a catch: what exactly are the “waters of the United States”? Rivers, streams, lakes, bays, and marshes obviously fit the bill. But what about a small creek that contains running water only a few months out of the year? Or a ditch beside the road that diverts runoff water after a big storm but is otherwise dry? Or what about a hole in your backyard that periodically collects a few inches of rainwater?

The answers to these questions are vital, because the EPA’s jurisdiction to enforce its strict permitting and polluting regulations extends only to what is officially considered “waters of the United States.” But you won’t find these answers in the Clean Water Act, because Congress wrote the law without defining “waters of the United States” or providing the EPA with any clear and precise standards to do so. This ambiguity in the law – and the immense discretion enjoyed by the EPA as a result – is problematic for two main reasons.

First, by telling the EPA to regulate a thing without strictly defining what that thing is, Congress effectively gave the bureaucratic agency the power to make the law and to enforce it. You don’t need to be a cynic to see that such a concentration of power within a single government agency – especially one that is run by individuals who don’t have to stand for election and whose names the American people will never know – is a recipe for abuse and corruption.

Moreover, an executive agency that has the power to define something also has the power to redefine it, again and again. This is exactly what has happened with the Clean Water Act. Over the years, EPA regulators have interpreted – and repeatedly reinterpreted – the law to accommodate their ever-expanding conception of their own power. This process reached the point of absurdity under President Obama when the EPA issued a rule, commonly called the “Waters of the United States rule,” that expanded its reach so far that it claimed it could regulate a hole in someone’s backyard that fills with rainwater in the winter, even if it is situated miles away from a stream that leads into a river.

For left-wing environmental groups, the open-ended nature of the Clean Water Act has been a dream come true, providing endless opportunities to steadily expand the federal government’s control of public and private lands. But for many Americans – everyone from farmers and ranchers to ordinary homeowners – the EPA’s evolving definition of “waters of the United States” has been a nightmare. If you’re required to obtain a permit from the EPA in order to lawfully fill a hole in your backyard with dirt, and if the EPA has the power to fine you tens of thousands of dollars a day for building a pond on your farm, are your private-property rights not under attack?

Thankfully, this week President Trump signed an executive order that requires the EPA to revise the Obama administration’s rule according to the standard set forth by the late Supreme Court Justice Antonin Scalia. In Rapanos v. U.S., Justice Scalia proposed defining “waters of the United States” to mean “only relatively permanent, standing or flowing bodies of water” not including “channels through which water flows intermittently or ephemerally, or channels that periodically provide drainage for rainfall.”

President Trump’s executive order is a tremendous first step toward bring clarity and commonsense to the Clean Water Act. But ultimately, this is a mess that only Congress can fix, which is why I will continue to try to advance legislative reforms, like those offered by Senators Barrasso and Paul, that will prevent the EPA from abusing its powers, while ensuring the agency still has the tools and resources it needs to help maintain a clean and healthy water supply in the United States.