Background
The Casper Aquifer underlies Albany County east of Laramie and supplies drinking water to thousands of city and county residents. Following the Wyoming Department of Environmental Quality’s (WDEQ) approval of a hydrogeologic Delineation Report, the Albany County Board of County Commissioners (Board) adopted the Casper Aquifer Protection Plan (CAPP) in 2002 and created the Aquifer Protection Overlay Zone (APOZ) — a specialized zoning overlay restricting certain land uses and development densities within the aquifer’s recharge area to protect groundwater from contamination by septic systems.
In 2023, the Board amended the APOZ to add, among other changes, a 35-acre minimum lot size requirement within the zone, citing studies showing that higher densities of on-lot septic systems increase nitrate loading to the aquifer. A coalition of ranching entities and individual property owners — led by Warren Livestock, LLC and the Bienz family — sought judicial review under the Wyoming Administrative Procedure Act (WAPA), challenging the amendments on four grounds: (1) the Board lacked statutory authority to use zoning as a vehicle for water quality regulation; (2) the APOZ’s distinct boundary-amendment procedures violated Wyoming’s constitutional equal protection guarantee; (3) the arbitrary and capricious standard of review does not apply to legislative agency action; and (4) the 35-acre lot size was arbitrary and capricious regardless. The district court upheld the amendments but declined to apply the arbitrary and capricious standard, concluding that standard was reserved for adjudicatory proceedings.
This was the second trip to the Wyoming Supreme Court. In Bienz v. Board of County Commissioners, 2024 WY 102 (Bienz I), the court had held that administrative legislative actions are reviewable under WAPA — overturning the trial court’s jurisdictional dismissal — and remanded for merits consideration. On remand, the district court applied authority, equal protection, and arbitrariness review, but excluded the arbitrary and capricious standard. Both sides appealed.
The Court’s Holding
Affirmed on all grounds. Writing for the majority, Justice Gray resolved each issue in the Board’s favor.
Authority to zone for aquifer protection. Wyo. Stat. Ann. § 18-5-201 grants counties broad authority to regulate land use to promote “the public health, safety, morals and general welfare.” The court held that protecting the Casper Aquifer plainly falls within that grant. The WDEQ’s authority over water quality under the Environmental Quality Act (EQA) does not preempt county zoning. The EQA expressly contemplates local participation through delegation and cooperative standards, and WDEQ itself had encouraged Albany County to adopt additional protective measures. The 35-acre lot size does not conflict with subdivision permit statutes or WDEQ rules: those provisions set minimum standards for sewage and water supply systems in individual permit applications; they do not preempt land use restrictions imposed by overlay zoning. Justice Hill dissented on this issue alone, arguing that the EQA’s comprehensive and exclusive grant of water quality authority to WDEQ — reinforced by the Legislature’s explicit, limited delegations to local governments when it wanted them involved — was not intended to be supplemented by an implied grant buried in a general land use statute that does not even contain the word “water.”
Equal protection. The APOZ boundary-amendment procedures differ from those governing standard zoning district amendments, but the court found a rational basis for the distinction: overlay zones serve a specialized protective function distinguishable from underlying zoning districts, and treating their boundary-change process differently is rationally related to the legitimate interest in protecting the aquifer. A sub-argument challenging a “previously surveyed parcels” limitation in the original 2023 text was dismissed as moot after the Board’s 2024 and 2025 amendments eliminated that provision.
Arbitrary and capricious standard extends to rulemaking. Resolving an open question in Wyoming administrative law, the court held that the arbitrary and capricious standard applies to agency legislative action — including county zoning amendments — not merely to informal adjudications. Wyo. Stat. Ann. § 16-3-114(c)(ii)(A) directs courts to set aside “arbitrary, capricious” agency action without drawing any line between legislative and adjudicatory proceedings. Drawing on federal APA precedent, particularly Motor Vehicle Manufacturers Association v. State Farm Mutual Auto Insurance Co., 463 U.S. 29 (1983), the majority held that agency action not developed on a formal, closed evidentiary record is reviewed for arbitrariness and caprice; only formal contested-case evidentiary findings trigger the more demanding substantial evidence standard (itself supplemented by an arbitrariness safety net). The district court erred in declining to apply the standard.
Not arbitrary and capricious. The APOZ amendments survived deferential rational-basis review. Studies in the record — including the 2011 CAPP, a 2013 engineering analysis finding that low precipitation rates require large lot sizes to dilute nitrate concentrations, the 2019 Wenck single-system septic study, and the 2020 Wenck nitrate-loading model — all supported the conclusion that higher septic density increases nitrate risk and that 35-acre lots would reduce contamination. Property owners’ contrary evidence showed a difference of scientific opinion, not a lack of rational basis. The 35-acre minimum does not effectively rezone APOZ land as agricultural (underlying use is still governed by the base zoning district); does not conflict with Wyo. Stat. Ann. § 18-5-201 (which preserves exemptions for family-gift lot splits); and does not require the Board to formally find a specific risk level before acting.
Chief Justice Boomgaarden, joined by Justice Fenn, specially concurred to emphasize that the WAPA’s plain text alone compels the arbitrary and capricious standard for all agency action. He cautioned that the majority’s additional framework — distinguishing “open-record” legislative action from formal adjudicatory proceedings — risks reintroducing the formal/informal confusion that Bienz I was meant to eliminate.
Key Takeaways
- Wyoming counties may use their general zoning authority under Wyo. Stat. Ann. § 18-5-201 to protect groundwater quality — including by imposing minimum lot sizes in aquifer recharge areas — without separate legislative authorization. WDEQ’s water quality jurisdiction and county zoning power operate in parallel, not in conflict, where the county acts through land use restrictions rather than discharge permitting.
- The Wyoming Supreme Court now definitively holds, in a published opinion, that the arbitrary and capricious standard of review applies to all agency rulemaking and legislative action under WAPA. Practitioners litigating challenges to zoning amendments, board resolutions, or other legislative-type agency action should frame their claims under this standard.
- Aquifer protection overlay zones may adopt boundary-amendment procedures distinct from those governing underlying zoning districts without violating Wyoming’s equal protection guarantee, so long as the distinction is rationally related to the overlay’s specialized purpose.
- An expectation of future development — including the ability to subdivide land — is not a vested property right under Wyoming law. Zoning changes that create nonconforming uses or foreclose anticipated subdivisions are not arbitrary as a matter of law.
- Justice Hill’s dissent keeps alive the argument that WDEQ’s comprehensive statutory mandate over water quality forecloses county zoning regulations whose operative purpose is water quality control rather than land use management. Future challenges in cases with a cleaner factual record may revisit that boundary.
Why It Matters
For Wyoming land use and environmental practitioners, Warren Livestock is the clearest statement yet that county boards can deploy their zoning power to protect local water resources alongside — not in conflict with — WDEQ’s regulatory scheme. Developers, ranchers, and rural property owners in aquifer recharge areas across Wyoming should expect that protective overlay zones backed by credible scientific records will survive WAPA challenge, even when the underlying science is disputed. Practitioners advising clients before county boards should counsel them to build an administrative record that traces rational connections between the data before the board and the specific regulatory choice made; under deferential arbitrary and capricious review, it is not enough to show the board could have chosen differently.
On Wyoming administrative law, the majority’s confirmation that the arbitrary and capricious standard applies to all legislative agency action fills the central gap left open by Bienz I and equips litigants with a well-developed body of federal precedent for framing WAPA challenges. The Chief Justice’s concurrence — favoring the WAPA’s plain text over a more elaborate analytical framework — signals a court inclination toward keeping administrative review doctrine lean. Practitioners should lead with the statute and treat the majority’s open-record/closed-record distinction as a secondary analytical layer, not a threshold classification exercise.