Supreme Court of Utah
615 P.2d 1265 (1980)
To invoke zoning estoppel, a local zoning authority must have committed an act or omission upon which the property owner could rely in good faith in making substantial changes in position or incurring extensive expenses.
The action upon which reliance is claimed must be clear, definite, and affirmative. Reliance on an omission must be based on a failure to act when the local zoning authority had a duty to do so.
The property owner is obligated to inquire and confer with the local zoning authority regarding the uses permitted on the property.