Most of the country is now subject to an Obama-era regulation defining the reach of the nation’s water-pollution law. But the regulation faces a bevy of legal challenges across the U.S. in a process that promises to be a chaotic process.

The Waters of the United States rule instituted late in President Barack Obama’s administration would give the Environmental Protection Administration (EPA) and the U.S. Army Corps of Engineers broad jurisdiction over the Clean Water Act. The rule could lead to a drastic increase in POTW enforcement of water discharges from plants in the linen, uniform and facility services industry ...