Supreme Court hands environmentalists a win in water pollution case.

The Supreme Court on Thursday sided with environmentalists by giving a broad reading to the types of water-borne pollution covered by the Clean Water Act.

In a 6-3 decision, the justices held that a permit is required for either a direct discharge of pollutants into federally regulated rivers and oceans or its “functional equivalent.”

“Suppose, for example, that a sewage treatment plant discharges polluted water into the ground where it mixes with groundwater, which, in turn, flows into a navigable river, or perhaps the ocean,” Justice Stephen Breyer wrote for the majority.

“Must the plant’s owner seek an EPA permit before emitting the pollutant?” he continued, referring to the Environmental Protection Agency. “We conclude that [a permit is required] if the addition of the pollutants through groundwater is the functional equivalent of a direct discharge from the point source into navigable waters.”

At issue in the case was whether Maui County in Hawaii violated the Clean Water Act, the landmark 1972 environmental law, by injecting wastewater underground without a permit that then seeped into the Pacific Ocean.