Q2 Quarterly Gas Infrastructure Litigation Update

Originally published for customers June 5, 2026.

What’s the issue?

The gas infrastructure litigation landscape continues to evolve, with new cases emerging, existing challenges advancing toward decision, and several disputes narrowing or being dismissed.

Why does it matter?

Litigation remains fragmented across courts and procedural stages, making it difficult to track which cases are advancing, which are newly emerging, and which risks are beginning to recede.

What’s our view?

The second quarter saw gas infrastructure litigation become both broader and more mature, with new cases emerging while several existing disputes advanced toward substantive decisions.

This is our second quarterly litigation update tracking legal challenges affecting interstate natural gas pipelines and LNG infrastructure. Each update draws on Arbo’s litigation tracking and analysis, focusing on what has changed since the last update, which cases are advancing, and where litigation is affecting project timing and execution. Individual cases continue to be analyzed in depth through separate Insights articles as they progress. This series focuses on movement across the broader litigation landscape and how project risk profiles are changing over time.

1. Cases Advancing (Briefing to Oral Argument)

Rio Grande LNG / Rio Bravo Pipeline (D.C. Circuit)

Since the last quarterly update, the challenge to FERC’s order on remand reaffirming its authorization of the LNG terminal and associated pipeline has advanced from early-stage litigation into merits briefing. Petitioners filed their opening brief on May 4, raising challenges to FERC’s NEPA analysis of the carbon capture and storage facility, including whether it should have been analyzed as a design alternative, connected action, or cumulative effect. FERC’s air quality analysis was also challenged, and several issues tied to the Supreme Court’s Seven County decision were raised regarding the Commission’s duty to ask about project plans instead of speculating.

The case remains one of the first major opportunities for petitioners to test post-Seven County NEPA arguments in the D.C. Circuit. This post compares how the court may apply Seven County‘s limits on agency speculation: Two Paths to Deference: The Fifth Circuit Charts FERC’s Authority on NEPA and Rates.

CP2 (FERC Certificate, DOE Authorization, D.C. Circuit)

Since the last update, oral argument has been held in the challenge to FERC’s authorization of the CP2 LNG terminal. The case is now awaiting a decision. As discussed in 2026 Watchlist: Projects, Permits, Power and Progressive Risk, the case resumed on the merits following DOE’s non-FTA authorization.

A separate D.C. Circuit case challenges DOE’s use of a categorical exclusion for non-FTA export authorization rather than preparing an EA or EIS, as it historically has. As discussed in DOE Drew a Narrow NEPA Boundary for CP2. Will It Hold?, DOE’s approach relies on an expanded NEPA Categorical Exclusion covering natural gas exports and associated marine transport.

Since the last update, the statement of issues has been filed and a briefing schedule established. The litigation raises questions regarding DOE’s treatment of domestic natural gas price impacts, the scope of environmental effects considered in export authorizations, and the legality of DOE’s categorical exclusion both generally and as applied to CP2.

NESE (FERC Certificate Reissuance, CWA 401, Multiple Venues)

NESE litigation across three venues has continued to advance since the last update. The D.C. Circuit challenge to FERC’s certificate reissuance has moved beyond the motions stage, with final briefs due July 27, 2026. Meanwhile, briefing has been completed in both the New York and New Jersey Clean Water Act Section 401 appeals. The New York case has progressed further, with oral argument held on June 18, 2026, while the New Jersey appeal remains awaiting argument.

For context on NESE’s path to reissuance and the state permitting backdrop, see Miracle on Docket 101 — Part II: NESE’s Return. Arbo continues to monitor litigation related to New York’s climate law for any implications affecting the broader regional permitting environment.

Matterhorn (Section 311 Rates, Fifth Circuit)

Since the last update, the challenge to FERC’s rejection of Matterhorn’s proposed Section 311 rates has continued through merits briefing. The Commission adopted a bright-line requirement that pipelines electing Section 311 rates must use the straight fixed-variable methodology absent narrow exceptions. Petitioners have filed their opening brief, Energy Transfer has submitted an amicus brief, and the petitioner’s reply brief is due July 13, 2026.

2. Early-Stage Litigation (Motions / Initial Posture)

Constitution (FERC Certificate Reissuance, D.C. Circuit)

New litigation has emerged over Constitution’s certificate reissuance request. The dispute is not whether Constitution should be built, but whether FERC can continue considering the company’s 2025 reissuance petition after the Second Circuit vacated the original certificate and ordered the prior proceeding dismissed.

Petitioners argue FERC is violating the court’s mandate by continuing to consider the new petition. FERC responds that it complied with the mandate by dismissing the original proceeding and that nothing prohibits the Commission from considering a new filing. At its core, the case asks whether the Second Circuit’s mandate merely closed the original proceeding or also prevents FERC from considering a new Constitution application. No briefing schedule has been issued.

SESE (FERC Certificate, CWA 404, Multiple Venues)

Three cases have now emerged related to the Southeast Supply Enhancement project: two in the D.C. Circuit in addition to the Fourth Circuit case challenging the U.S. Army Corps of Engineers’ Section 404 permit.

In the D.C. Circuit, environmental petitioners challenge FERC’s market need determination as well as the Commission’s NEPA and greenhouse gas emissions analysis. Separately, Transco challenges FERC’s rolled-in rate determination. The court has not yet issued briefing schedules in either case.

In the Fourth Circuit, an environmental coalition challenging the Corps’ Section 404 permit sought both a temporary administrative stay and a stay pending appeal. The court denied both requests, and the case now proceeds to the merits, with final briefing scheduled for August 12, 2026.

MVP Southgate (FERC Certificate, CWA 401, Multiple Venues)

Three cases are currently pending for MVP Southgate. Two challenges to the project’s Clean Water Act Section 401 certifications are pending in the Fourth Circuit, while environmental organizations have also challenged FERC’s certificate order in the D.C. Circuit.

Since the last update, the Fourth Circuit denied a motion for stay pending appeal, allowing construction to continue while litigation proceeds. Final briefs are currently due July 28, 2026, for the Virginia challenge and August 18, 2026, for the North Carolina challenge.

Separately, environmental organizations have appealed FERC’s certificate order in the D.C. Circuit, raising issues related to market need, cumulative impacts, and greenhouse gas emissions. The court has not yet issued a briefing schedule.

Commonwealth LNG (Coastal Use Permit, 38th Judicial District Court, Parish of Cameron)

Louisiana court vacated Commonwealth LNG’s original coastal permit based on environmental justice and climate-related analysis. Louisiana then reissued the permit, prompting a new challenge. For detailed analysis of the first decision and its implications for state-level climate and EJ arguments, see Blurring Lines – Commonwealth LNG Climate and EJ Arguments Cross Into State Court. The principal issue Arbo continues to watch is how the court addresses arguments under Louisiana’s constitutional public trust doctrine and whether the reissued permit sufficiently addresses the deficiencies identified in the earlier proceeding.

3. Narrowing or Resolved Litigation in Coal to Gas

Since the last update, TVA has decided to continue operating the Cumberland and Kingston coal plants beyond 2028. Under TVA’s revised plans, new natural gas generation appears likely to be developed alongside the existing coal units rather than replacing them entirely.

These developments resulted in dismissal of the remaining litigation associated with Cumberland. At Ridgeline, however, the district court challenge to TVA’s NEPA review remains pending. Although the implications of TVA’s revised plans are still unclear, similar narrowing could be on the horizon. Separately, the Fifth Circuit case involving recovery of costs associated with a solar array was dismissed following FERC’s rehearing order.

If you would like to discuss how gas infrastructure litigation developments may affect project timing, permitting risk, or market opportunities, please contact us.