(CNN) — A majority of the Supreme Court seemed skeptical of the Biden administration’s defense of the Environmental Protection Agency’s authority to protect wetlands from pollution under the Clean Water Act on Monday, in the first session of oral arguments in the court’s new term.

At the same time, however, some conservatives on the bench seemed to reject an argument from an opposing lawyer suing the federal government that would severely limit EPA’s ability to regulate.

The long-running dispute centers on an Idaho couple who were hoping to build a home on new property in 2007 but received a stop work order from the EPA. The agency asserted that the property contained “navigable waters,” or wetlands subject to Clean Water Act protections.

Now, the justices are attempting to devise a test for determining when wetlands — such as swamps, bogs, marshes that are adjacent to navigable waters — fall under the EPA’s authority.

At her first oral arguments since joining the bench, Justice Ketanji Brown Jackson asked several questions, joined at times by the two other liberal justices, suggesting that Congress’ intent was clear. They pushed on the notion that a wetland doesn’t have to actually touch the surface of navigable waters in order to trigger government regulation.

Jackson did not hesitate to ask several questions, at one time interrupting another justice on the bench — a practice that rarely occurs now that the court has changed its process for questioning since the beginning of the Covid-19 pandemic.

At the end of arguments, she also broke from usual procedures by interrupting a lawyer during his rebuttal, a period of time where the justices usually allow a lawyer to have his final say. Chief Justice John Roberts offered the lawyer more time.

Jackson, a veteran of multi-member courts having served on a federal appellate court based in Washington DC, seemed at ease, at one point sharing a joke with her seatmate Brett Kavanaugh. She wore a lace jabot over her robe, reminiscent of collars once worn by Justice Ruth Bader Ginsburg.

The case before the justices has environmentalists — who were deeply disappointed last term when the court’s conservative majority curbed the agency’s authority to regulate power plant emissions — on edge. They see the current court as hostile to the power of federal agencies to protect the environment and fear the court will radically roll back federal safeguards for clean water, making it easier for oil and gas industries to bulldoze wetlands jeopardizing waterways.

The Clean Water Act allows the Environmental Protection Agency to regulate “waters of the United States,” but the exact definition of such waters remains unclear. Critics of the EPA’s position cast the dispute as a battle of landowners across the country seeking to make use of their property without the interference of overzealous federal regulators.

Fight over home in Idaho

In 2004, Chantell and Michael Sackett purchased a vacant lot near Idaho’s Priest Lake. Three years later they broke ground, hoping to build a family home, but soon got entangled in a regulatory dispute. As they began backfilling the property with 1,700 cubic yards of sand and gravel to create a stable grade, the EPA sent them an order halting construction.

At one point, the Sacketts were ordered to take actions to restore the site and were told if they did not, they could be faced with penalties of over $40,000 per day. Their property is bounded by roads to the north and the south, but across the street is a man-made ditch that drains about 35 acres of wetlands. The necessary permit would cost thousands of dollars and takes around two years to obtain.

The Sacketts stressed that they had obtained all local building permits, that their site was bordered by developed properties and roads and that nothing in their deed suggested that their lot contained wetlands. They sued the EPA claiming that its jurisdiction under the law did not stretch to their property.

The Clean Water Act was passed to “restore and maintain the chemical, physical, and biological integrity of the Nation’s waters.” It extends to “all navigable waters” and prohibits individuals without permits from discharging pollutants including rocks and sand into those waters. Since the CWA was enacted, however, courts have struggled to identify the exact definition of “waters in the USA.”

Antonin Scalia’s test in Raponos

In a 2006 case called Rapanos v. United States, a fractured Supreme Court wiped away two decisions upholding the application of the Clean Water Act to wetlands connected to distant navigable waters via ditches and drains, but the justices divided over their rationale.

Justice Antonin Scalia, joined by only three justices, developed a test for determining whether wetlands could be regulated under the law. Scalia said that “waters of the United States” extend only to “relatively permanent, standing or flowing bodies of water” and to wetlands with a “continuous surface connection” to permanent waters.

In the lawsuit at hand, a lawyer for the Sacketts supports Scalia’s view and says the couple should prevail. The lawyer stressed that the Sackett property contains “no stream, river, lake or similar waterbody.”

Damien Schiff, a lawyer for the Sacketts, told the justices in court papers that his clients’ case is “emblematic of all that has gone wrong with the implementation of the Clean Water Act,” following the Supreme Court’s 2006 decision.

Schiff stressed that the Rapanos plurality written by Scalia meant that the wetlands on their property limited federal authority only to wetlands that have a continuous surface-water connection to regulated waters.

“The Clean Water Act does not regulate wetlands standing alone,” Schiff argued. “Rather, the Act reaches such non-waters only to the extent that a significant physical nexus (like a shoreline connection) between wetlands and an authentic water” such as a stream, river, ocean or lake, he said.

In court, Jackson challenged Schiff. “Let me try to bring some enlightenment to it by asking it this way,” she said.

“Why would Congress draw the coverage line between abutting wetlands and neighboring wetlands when the objective of the statute is to ensure the chemical, physical, and biological integrity of the nation’s waters?” she asked.

Anthony Kennedy’s language in Rapanos

The EPA, however, pointed to now retired Justice Anthony Kennedy’s reasoning in the Rapanos case and said it should prevail against the Sacketts under a so called “significant nexus test.”

Kennedy — whose wrote on the narrowest grounds supporting the majority’s bottom line—said that under the CWA, “jurisdiction over wetlands depends upon the existence of a significant nexus between the wetlands in question and navigable waters in the traditional sense.”

“Wetlands play an essential role in protecting the chemical, physical, and biological integrity of neighboring waterways, including by filtering pollutants, storing water, and providing flood control,” a Justice Department attorney said Monday.

A federal appeals court — relying upon Kennedy’s rationale — ruled in favor of the EPA.

“The record plainly supports EPA’s conclusion that the wetlands on the Sacketts property are adjacent to a jurisdictional tributary and that, together with the similarly situated Kalispell Bay Fen, they have a significant nexus to Priest Lake, a traditional navigable water,” the 9th US Circuit Court of Appeals held.

On Monday, Kennedy, who rarely appears at the court, sat in the audience — in a section of the court reserved for retired justices and special guests to hear oral arguments in the case that he had decided before his retirement.

(Copyright (c) 2024 CNN. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed.)

Join our Newsletter for the latest news right to your inbox