Sign regulation is a legitimate municipal function serving traffic safety and aesthetics, and the constitutional constraint is that regulations must generally avoid drawing distinctions based on the message.
Content-based on its face. A rule that requires reading the sign to know which regulation applies is content-based and faces strict scrutiny, which such ordinances rarely survive. Categories like political signs, real estate signs, directional signs for events, and ideological signs each treated differently is the classic defective structure.
What remains permissible. Distinctions based on size, height, location, illumination, materials, number per parcel, and the distinction between on- premises and off-premises signage, which has been treated as not facially content-based.
Commercial speech receives less protection, and regulation of commercial signage is analysed under an intermediate standard.
Temporary signs. Durational limits keyed to an event — removal within a period after an election — are content-based if they require reading the sign. Neutral durational rules for all temporary signs are the safer structure.
Permitting. Any prior approval requirement needs definite standards and short, fixed decision deadlines, or it operates as an unconstitutional prior restraint through delay.
Severability and grandfathering clauses, and a written record of the traffic and aesthetic justifications, are what allow an ordinance to survive partial invalidation.