The D.C. Circuit affirmed, in all but a few aspects, the district court’s dismissal of plaintiffs’ claims. It affirmed the dismissal of most of the Tribe’s RCRA claims under Section 113(h) of the Comprehensive Environmental Response, Compensation, and Liability Act (“CERCLA”), which deprives federal courts of jurisdiction to hear “challenges to removal or remedial action selected under” CERCLA. The court did, however, reject the government’s argument that a suit challenging EPA’s authority to invoke CERCLA is barred by Section 113(h), and expressed misgivings about possibility that Section 113(h) might allow EPA to delay remedial work at a site indefinitely. The D.C. Circuit also reversed the district court’s dismissal of another RCRA claim based on a release of liability in a cooperative agreement between the Tribe and the Department of Energy for the remediation of the uranium mill site, holding that the claim fell outside the scope of the release. The court denied the remaining claims under the Mill Tailings Act, the Indian Agricultural Act, and the Indian Dump Cleanup Act.

The most significant portion of the D.C. Circuit’s opinion is its ruling on the Tribe’s breach of trust claims, which had been asserted under the Administrative Procedure Act (“APA”). The Tribe argued that the trust-creating language of 25 U.S.C. § 640d-9(a) (providing that the lands at issue “shall be held in trust by the United States exclusively for the Navajo Tribe”), combined with the federal government’s actual use and control of the former mill sites and dumps, created an enforceable trust duty. The D.C. Circuit rejected the Tribe’s argument, finding the statute insufficient to create an enforceable trust.

Following Supreme Court case law addressing trust claims brought under the Indian Tucker Act, 28 U.S.C. § 1505, the D.C. Circuit acknowledged the “loose congruence” between the claims in United States v. White Mountain Apache Tribe, 537 U.S. 465, 475 (2003) ("White Mountain Apache Tribe"), and the instant case, as both cases involved trust lands allegedly under government control. The court ultimately determined, however, that the heightened requirements for breach of trust claims set forth in United States v. Navajo Nation, 556 U.S. 287 (2009) ("Navajo Nation"), ultimately controlled the resolution of this case and precluded finding an enforceable trust.