Environmental groups squared off against New Jersey regulators and a natural gas giant in a federal appeals court Wednesday, arguing a controversial interstate pipeline expansion was approved without required public scrutiny.

The legal battle before the U.S. Court of Appeals for the Third Circuit centers on the Northeast Supply Enhancement, a proposed extension of the Transcontinental Gas Pipe Line Company’s (Transco) 10,000-mile network.

The New Jersey Department of Environmental Protection (DEP) denied Transco’s water quality requests in 2019 and 2020 due to environmental flaws and a lack of public need.

However, the agency approved a nearly identical third application in 2025, merely requiring Transco to submit environmental monitoring plans before starting construction.

The Natural Resources Defense Council (NRDC) and New York-New Jersey Baywatch promptly sued, claiming the approval violated the Clean Water Act and the Administrative Procedure Act by cutting out the public.

"These errors show an agency struggling to get to 'Yes' and running roughshod over clear statutory requirements," NRDC attorney Jackson P. Garrity told the three-judge panel.

Baywatch attorney Kaitlin Morrison argued regulators concealed a vital 739-page stormwater management plan, which environmental groups only discovered during litigation.

U.S. Circuit Judge Cheryl Ann Krause questioned the legality of the approval, asking how bypassing public review on critical compliance plans was not "arbitrary and capricious."

DEP attorney Nathaniel F. Rubin defended the decision, arguing the agency acted lawfully because Transco cannot begin construction until the state approves the finalized monitoring plans.

Transco attorney Richard G. Scott added that both the company and the state fulfilled all legal notification requirements, noting no rule mandated additional public notice for the updated report.

The panel, which also included U.S. Circuit Judges Arianna J. Freeman and Jane R. Roth, took the case under advisement.

If completed, the pipeline would stretch from Lancaster County, Pennsylvania, under the Lower New York Bay, to New York City.