The Ninth Circuit has removed a long-standing obstacle that prevented private parties and local governments from intervening in National Environmental Policy Act (“NEPA”) cases. In Wilderness Society v. U.S. Forest Service, an en banc panel of the Ninth Circuit jettisoned the “federal defendant” rule, which allowed only the lead federal agency to defend a NEPA case and precluded other parties, who often had significant interests at stake, from intervening as of right in the lawsuit. The decision sets the stage for increased participation in NEPA litigation by a wide variety of businesses, trade associations, state and local governments, and other third parties with a significantly protectable interest in the outcome.

In determining whether to allow a third party to intervene in litigation, federal courts apply Federal Rule of Civil Procedure 24(a)(2). The rule provides for intervention when a party (1) timely files a motion to intervene; (2) claims a “significantly protectable” interest relating to the property or transaction at issue; and (3) claims an interest that is inadequately represented by the parties to the action. Courts have looked to practical and equitable considerations to construe the rule broadly in favor of proposed intervenors.