PHOENIX — An Arizona trial court has struck down a controversial water regulation that had significantly restricted new home construction in the Phoenix metropolitan area, marking a major legal victory for developers and housing advocates.
The ruling invalidates the so-called “Unmet Demand Rule,” implemented by the Arizona Department of Water Resources, which required developers to demonstrate a 100-year water supply not just for individual projects but across the entire regional “active management area.”
A judge in Maricopa County determined that the agency “did not comply” with state law when implementing the rule, effectively rendering the restrictions unenforceable.
The policy dramatically altered development requirements in the fast-growing Phoenix region, one of the nation’s most active residential construction markets. Previously, Arizona law required builders to ensure adequate groundwater supply for specific developments. The updated rule expanded that requirement to cover the entire regional water system.
Because the designated management area spans a region comparable in size to Connecticut, the rule created significant hurdles for developers attempting to secure approvals. Critics argued that it effectively halted new housing construction at a time when supply constraints were already driving up home prices.
The lawsuit challenging the rule was brought by the Home Builders Association of Central Arizona and supported by the Goldwater Institute.
In its decision, the court found that the agency exceeded its authority by introducing new criteria without following required rulemaking procedures. The judge noted that the department applied standards “that did not previously exist” while claiming to enforce existing law.
The ruling also emphasized that administrative agencies must adhere to established legal processes when implementing policy changes, particularly those with far-reaching economic impacts.
According to the decision, the expanded definition of the affected area created additional barriers for developers seeking necessary approvals and contributed to a slowdown in construction activity.
Supporters of the challenge argued that the rule imposed unnecessary restrictions despite the availability of water resources sufficient to support development under existing regulations.
The case highlights broader tensions between resource management and housing growth in arid regions, where water availability remains a central concern for long-term planning.
With the rule now invalidated, developers may regain momentum in the Phoenix-area housing market, although future regulatory actions could continue to shape construction activity in the region.
Originally reported by Timothy Sandefur in Gold Water Institute.
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