Everyone knows Chevron and Auer deference, where federal courts defer to reasonable agency interpretations of ambiguous statutes and rules. State courts, too, often similarly defer. The arguments for and against these deference doctrines are well known.

Much lesser known is how state (and even federal) courts regularly defer to municipalities’ interpretations of their own ordinances. Although lesser known, deference to municipal interpretation is no less significant: local governments exercise great power over the lives of their constituents. Disputes about land use, public health, economic regulation, and public accommodations frequently implicate ordinance interpretation, along with any corresponding judicial deference.

I explore this issue in a new article in the Fordham Urban Law Journal, using Wisconsin law as a primary case study. Before 2018, Wisconsin courts deferred to agency interpretations of statutes and rules. But in 2018 in Tetra Tech v. Dep’t of Revenue, the Wisconsin Supreme Court ended that practice. For several years, Wisconsin courts have also deferred to municipalities’ interpretations of ordinances.

I argue that all of Tetra Tech’s bases for assailing agency deference—constitutional structure, due process, and prudential concerns—also apply to municipal deference. Based on Tetra Tech, then, municipal deference must fall—or already has fallen, not only in Wisconsin but also in other similarly situated states. Utah and Mississippi, for their part, have followed that exact path.

Joseph S. Diedrich is a senior associate at Husch Blackwell LLP, where he specializes in appellate litigation and administrative law.