Accessory dwelling units have been the subject of state legislation in many jurisdictions, constraining what local governments may require.
State preemption. Statutes commonly require that units be permitted by right in single-family districts, limit review to objective standards, prohibit owner occupancy requirements in some states, cap fees, restrict parking requirements, and impose short decision deadlines with deemed approval.
What local governments may still regulate. Objective standards on size, height, setbacks consistent with statutory limits, design consistent with the principal dwelling, and building code compliance.
What is commonly preempted. Discretionary review, minimum lot size requirements above a threshold, replacement parking, and conditional use processes.
Short-term rental interaction. Many statutes permit local governments to prohibit the use of an accessory unit as a short-term rental, which is the principal remaining local control.
Utility connections and fees. Restrictions on requiring separate connections and on capacity charges for units below a size.
Practical drafting. Where a state mandate applies, an ordinance that has not been updated is unenforceable in part, and applications must be processed under the statute regardless of what the ordinance says. Reviewing the ordinance against the current statute is the first step.