The U.S. Supreme Court on Thursday reined in the Environmental Protection Agency’s broad regulation of wetlands, saying the agency’s statutory authority to prevent pollution of “waters of the United States” generally does not extend to entities that feed those waterways.

In its fractured decision, the high court stopped EPA’s enforcement action against an Idaho couple for having dumped dirt near a ditch that led to a creek which fed into Priest Lake, an interstate waterway covered under the federal Clean Water Act. The court said the ditch was too far removed—both geographically and statutorily—from the lake.