The Clean Water Act (CWA), which took shape during the early 1970s, bans the dumping of pollutants directly into surface waters, ranging from wetlands and rivers to oceans. Whether the federal law’s prohibition also should apply to indirect dumping that has the same effect is a matter expected to go before the nation’s highest court later this year.

At the center of the debate is Maui’s Lahaina Wastewater Reclamation Facility, which injects a daily average of at least 3 million gallons of treated sewage into groundwater that flows toward the ocean.

Last March, the 9th U.S. Circuit Court of Appeals ruled that Maui County has been violating the CWA since the facility’s operations started in the early 1980s. Maui County appealed to the Supreme Court; if it wins, the impacts for water pollution rules nationwide could be huge.

That would be an unfortunate outcome: In Maui, the scientific evidence demonstrates that treated sewage dumped into injection wells is seeping into the ocean, killing coral and triggering algae blooms.

In 2011, amid growing concerns about proliferating algae blooms that smother reefs and other degradation, University of Hawaii scientists initiated a tracer-dye study that conclusively linked treatment-plant discharge with tainted near-shore waters. And last year, U.S. Geological Survey research found that discharge from injection wells — positioned about a half-mile from the shoreline — has been drastically undermining the area for years.

The 9th Circuit’s opinion against Maui rightly concluded: “At bottom, this case is about preventing the county from doing indirectly that which it cannot do directly.” Under federal law, a National Pollutant Discharge Elimination System (NPDES) permit is needed to dispose of the wastewater in ocean waters.

In 2018, another appellate court interpreted the law in the opposite way. In a Kentucky case, pollutants from coal ash retention ponds seeped into groundwater that fed waterways. The 6th Circuit Court ruled that only pollutants added directly to navigable bodies of water are regulated under the law.

The split in opinion helped pave the way for the U.S. Supreme Court to take up the Maui case, in which the county asserts that because it’s not directly pouring pollutants into near-shore waters, no NPDES permit is needed.

The county contends that from its perspective, West Maui’s coral is generally in healthy condition, with sites including Kahekili — downstream from the wastewater facility — tagged as “pristine.” The county maintains that groundwater regulation should be handled as a “home-rule” issue as pollution-related challenges vary from place to place.

The U.S. Environmental Protection Agency’s acting administrator, Andrew Wheeler, seems to support this take. And it’s a given that if the Supreme Court reverses the 9th Circuit’s ruling, supporters of President Donald Trump’s efforts to roll back the Obama era’s stepped-up environmental regulation likely will cheer a perceived correction of federal overreach.

But in this case, amid growing concerns tied to climate change and ocean acidification, weaker federal law would open a door to potentially accelerating pollution- related troubles here and elsewhere. That would be a step backward for environmental stewardship, but it’s a possibility due to the current makeup of the high court.

Earth­justice, which is representing Maui community groups — Hawai‘i Wildlife Fund, Sierra Club-Maui Group, Surfrider Foundation and West Maui Preservation — in the ongoing legal debate, has rightly pointed out that we could see industries quickly assuming effective free rein to discharge pollutants indirectly into the nation’s waterways.

It’s disappointing that Maui is continuing to side-step the pollution problem. If politics prevails over science in a ruling from the Supreme Court, heightened vigilance in safeguarding Hawaii’s near-shore ecosystems from land-based sources of pollution will fall squarely on county and state governments.