Thursday’s Supreme Court ruling on the Clean Water Act will require permits and limits for polluters, but will ultimately still allow them to discharge pollution into streams that are connected to major U.S. waterways.

The high court, in a 6-3 decision, struck down the Environmental Protection Agency’s 2019 interpretation of the Clean Water Act, which aimed to exclude pollution that moves through groundwater from the legislation’s permitting requirements.

“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,” the majority opinion stated.

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Water quality advocates say, however, that those permits can be easy to come by, so the ruling won’t necessarily prevent facilities from polluting entirely, though it will require them to comply with limits established in the permits.

“It is possible that the same facilities that might have otherwise presumed themselves to be exempt, will be able to discharge and will get permits to do so, but in that process, will have pollution limits on what they’re discharging, and that’s a very significant improvement,” said Jon Devine, the director of federal water policy at the Natural Resources Defense Council.

He said that under the interpretation that was struck down, there was a loophole that would allow facilities to “determine for themselves” whether they needed to seek a permit.

An EPA official told The Hill in an email that the agency was “reviewing the decision and the Court’s call for the Agency to provide further guidance.”

“In holding that the Clean Water Act requires a permit for the addition of pollutants to groundwater if it is the “functional equivalent” of a direct discharge, the Court unfortunately leaves some uncertainty for the public, including private property owners,” the person said.

The decision also comes on the heels of the finalization of a separate Trump administration rule called the Navigable Waters Protection Rule, which removes protections for smaller bodies of water that environmentalists say should be protected to stop pollution from reaching larger water sources.

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Earthjustice attorney David Henkin, who argued the Supreme Court case, said that the new decision is interrelated with the navigable waters rule because the court’s decision means that facilities need a permit to discharge mobile pollution into some smaller bodies of water.

“It’s a bad thing,” Henkin said of the Navigable Waters Protection Rule. “Yesterday’s Supreme Court decision made that bad thing a little bit less bad because polluters will not be able to stick their pipes into them and put mobile pollutants into them.”

Proponents have defended the navigable waters rule, saying that a previous Obama administration rule it replaced was too far-reaching.

The Supreme Court ruling came after environmental groups in Hawaii sued Maui County over a municipal water treatment plant that was pouring wastewater into wells, where it combined with groundwater. A study had also found that some of the wastewater had surfaced near beaches.