Key Points

  • The Fifth Circuit reversed the Western District of Texas's denial of the Center for Biological Diversity's motion to intervene of right in Texas's challenge to the dunes sagebrush lizard's endangered listing.
  • The panel held that the Center rebutted the presumption of adequate representation because it and the federal government disagree about whether the listing is lawful at all.
  • The Center relied on changed agency priorities, the government's abandonment of similarly situated Endangered Species Act listings, and the government's decision to settle and vacate the lizard listing.
  • The panel followed the Fifth Circuit's September 2026 decision in State of Texas v. U.S. Department of Interior, which granted the Center intervention to defend the lesser prairie-chicken listing.
  • The panel found the Center's motion timely, its interest sufficient and that interest at risk of impairment, and remanded the case to the district court.

A federal appeals court ruled Nov. 6 that the Center for Biological Diversity may join Texas's lawsuit over the dunes sagebrush lizard to defend the reptile's endangered-species listing, holding that the federal government, which has decided to settle the case and vacate the listing, does not adequately represent the group's interests.

A three-judge panel of the U.S. Court of Appeals for the Fifth Circuit, Circuit Judges Smith, Graves and Ho, reversed an order of the U.S. District Court for the Western District of Texas that had denied the group's motion to intervene. The unsigned, per curiam opinion is not designated for publication. The panel sent the case back to the district court.

The decision puts the environmental group into a case in which the government has decided to settle and vacate the listing the group wants to keep. The panel rested its ruling on a September decision by another Fifth Circuit panel, State of Texas v. U.S. Department of Interior, which let the Center intervene to defend the listing of the lesser prairie-chicken. That decision, the panel wrote, "governs our consideration of this case."

The dispute began on May 20, 2024, when the U.S. Fish and Wildlife Service published a final rule listing the dunes sagebrush lizard as endangered under the Endangered Species Act. Shortly afterward, Texas sued to overturn the listing, arguing that it violated the Service's policies, its rules and the statute.

In March 2025, "following the change in presidential administration," the Center moved to intervene under Federal Rule of Civil Procedure 24(a). The group, which the opinion says worked for years to secure federal protection for the lizard and filed the listing petition, sought to help defend the rule. It also sought permissive intervention under Rule 24(b), but it did not press that request on appeal.

To intervene as of right, a party must show that its application is timely, that it has an interest in the subject of the lawsuit, that the outcome may impair its ability to protect that interest, and that "its interest is inadequately represented by the existing parties to the suit." The district court addressed only the last of those requirements and found that the government defendants adequately represented the Center.

The district court reasoned that the Center, like the government, sought to "uphold the Final Rule and maintain the dunes sagebrush lizard's endangered status." It said that President Trump's policy statements about promoting American energy through reconsidering species listings showed nothing more than a "mere possibility of divergent interests at some point in the future," and it faulted the Center for failing to identify specific conduct showing inadequate representation.

The Fifth Circuit presumes that representation is adequate in two situations: when the would-be intervenor has the same ultimate objective as an existing party, and when a government body or officer is charged by law with representing the intervenor's interests. The burden of showing inadequate representation is typically "minimal," the panel said, quoting circuit precedent, though "it cannot be treated as so minimal as to write the requirement completely out of the rule."

The panel held that the district court "overstates the Center's burden for overcoming the presumption of adequate representation," and that "it understates the divergence between the Center's interest and that of the Government." Quoting the prairie-chicken decision, the panel wrote that an intervenor "need only point to specific conduct showing that the party at issue inadequately represents their [interest], notwithstanding that it shares an ultimate objective."

In the prairie-chicken case, the intervenors had pointed to "announced changes in agency priorities" and "the Government's efforts to vacate the Listing Rule at issue." Those facts, the panel wrote, showed disagreement on "the core question of whether the Listing Rule's protections . . . are lawful at all."

"So too here," the panel wrote. The Center cited changes in agency priorities and the government's abandonment of similarly situated Endangered Species Act listings in the prairie-chicken litigation and in litigation over Central Texas mussels pending in the Northern District of Texas. The group also pointed to the government's decision to settle and vacate the lizard listing itself.

"In short, the Center and the Government disagree about whether the Lizard's listing is lawful at all—the core issue in this case," the panel wrote. That disagreement, it held, rebutted the presumption of adequate representation.

The panel then took up the three requirements the district court had not reached and found each satisfied. The Center's motion was timely, the panel held, because it came early in the litigation, before the deadline for adding new parties and before the filing of the administrative record. The district court had likewise observed that timeliness was not an issue, and Texas did not dispute it.

The panel held that the Center has an interest in the case because of its years of work to win protection for the lizard and its listing petition. The district court had assumed that interest without deciding it, and Texas did not object.

On the final element, the panel held that the outcome of the case may impede the Center's ability to protect the listing. "An adverse result in the underlying case may vacate, remand or otherwise weaken the listing rule—the very thing the Center seeks to protect in this litigation," the panel wrote. Texas did not contest that point either.

The panel concluded that the Center "satisfies the requirements for intervention of right." It reversed the denial of the motion to intervene and remanded the case, No. 7:24-CV-233, to the Western District of Texas "for proceedings consistent with this opinion."