Cities and towns may enact laws that restrict the number and types of animals a person may own. This is done to protect property owners from nuisances (unlawful interference with the use and enjoyment of a personís land), such as unpleasant odors and noise made by animals. Pet owners feel that such restrictions impact their property rights, as pets are considered personal property by law. Pet owners also argue that limiting the number of pets does not necessarily decrease any nuisance to other residents. Ordinances that state a certain number of animals are a nuisance must show that a nuisance actually exists, or they may be struck down.
Laws that limit the number of pets one may own will generally be upheld if they are rationally related to furthering the goals of protecting the public health, safety, and welfare. In contrast, laws that restrict ownership based on specific characteristics of pets, such as weight, may not be upheld because weight may change.
Ordinances that impose criminal penalties for violations are interpreted by courts in favor of pet owners. In addition, pet owners may be able to use zoning laws as a defense against prosecution. For example, if the pet owner can show that he owned a certain number or type of animals before the pet ownership law was enacted, then his situation could be considered a prior non-conforming use. However, once an ordinance is enacted that changes a once lawful activity into an unlawful nuisance, the prior lawful use must stop, or the pet owner may be charged with a violation.
Some cities and towns have attempted to address pet nuisance issues by limiting the number of pets a person can own, usually to 3 or 4 animals. While these ordinances are sometimes challenged by pet owners, courts usually uphold the laws as reasonable.