Pasqua Yaqui Tribe v. United States Environmental Protection Agency, 557 F.Supp.3d 949

Plaintiffs (six tribes) challenged two agency actions redefining “waters of the United States”: the 2019 Repeal Rule (which reinstated pre-2015 regulations) and the 2020 Navigable Waters Protection Rule (NWPR) (which narrowed the definition).
Plaintiffs moved for summary judgment; Agencies instead sought voluntary remand of the NWPR without vacatur while they revise the rule. Intervenors split: Sacketts opposed remand; business intervenors opposed vacatur.
NWPR relied heavily on the Rapanos plurality approach, categorically excluded certain features (e.g., ephemeral streams), and the Agencies acknowledged scientific and effect-related concerns about the NWPR’s scope.
The Ninth Circuit treats Justice Kennedy’s Rapanos concurrence (the “significant nexus” test) as controlling precedent for fractured decisions, which undercut the Sacketts’ argument that the plurality governs.
The Court granted the Agencies’ voluntary remand request and, applying the equitable vacatur test, concluded the NWPR should be vacated because the rule contained serious substantive errors and remand without vacatur would risk environmental harm.
The Court dismissed Counts I–IV (NWPR claims), denied pending summary-judgment motions without prejudice, and ordered the parties to propose further proceedings on the 2019 Repeal Rule (Count V).

Issue	Plaintiff's Argument	Defendant's Argument	Held
1. Should the Agencies’ request for voluntary remand of the NWPR be granted?	Plaintiffs do not oppose remand.	Agencies requested remand to revise/replace NWPR.	Granted.
2. If remand is granted, should the NWPR be vacated?	Plaintiffs: vacatur needed to prevent irreversible environmental harm.	Agencies did not request vacatur; intervenors opposed vacatur.	Vacatur ordered.
3. Did the NWPR contain serious procedural or substantive errors (arbitrary and capricious)?	NWPR ignored science, Agencies’ experts, and majority Rapanos positions; undermines CWA objectives.	Agencies acknowledge substantial concerns and will reconsider.	Court found substantive, noncurable errors supporting vacatur.
4. Does the Rapanos plurality control and constrain the Agencies’ permissible definition?	Sacketts: plurality controls, limiting Agencies to Scalia test.	Agencies and Plaintiffs: Kennedy concurrence controls under Ninth Circuit precedent.	Court rejected Sacketts’ claim; Kennedy rule governs; remand appropriate.

Rapanos v. United States, 547 U.S. 715 (2006) (plurality and Kennedy concurrence set competing tests for CWA jurisdiction over wetlands)
Motor Vehicle Mfrs. Ass'n v. State Farm Mut. Auto. Ins. Co., 463 U.S. 29 (1983) (arbitrary-and-capricious standard for agency action)
Chevron U.S.A., Inc. v. Nat. Res. Def. Council, Inc., 467 U.S. 837 (1984) (agency statutory-interpretation deference framework)
Cal. Cmtys. Against Toxics v. EPA, 688 F.3d 989 (9th Cir. 2012) (standards for voluntary remand and vacatur analysis)
Pollinator Stewardship Council v. EPA, 806 F.3d 520 (9th Cir. 2015) (vacatur appropriate when leaving rule would risk environmental harm)
Nat. Res. Def. Council, Inc. v. Pritzker, 828 F.3d 1125 (9th Cir. 2016) (agency conclusions that conflict with its experts can be arbitrary and capricious)
Encino Motorcars, LLC v. Navarro, 136 S. Ct. 2117 (2016) (agency must provide reasoned explanation for changes in policy)
Nat. Res. Def. Council v. Wheeler, 955 F.3d 68 (D.C. Cir. 2020) (vacatur consequences and regulatory uncertainty considerations)