Environmental groups trying to stop the unintentional transfer of invasive species from foreign bodies of water into U.S. waterways have won a shot at tougher regulations with a decision by the U.S. Court of Appeals for the Second Circuit.

The circuit held that the U.S. Environmental Protection Agency acted arbitrarily and capriciously in 2013 by granting a general permit regulating the discharge of ballast water by ships under the Clean Water Act and ordered the agency to rewrite the permit.