What types of "families" can cities exclude?

Last year, the Iowa Supreme Court decided the case of Ames Rental Property Ass'n v. City of Ames, which addressed the issue of what is a "family."  Ames, in an effort to prevent groups of Iowa State students from living in residential areas, passed an ordinance restricting the kinds of living arrangements allowed in certain areas of the City.  

Specifically, in low density residential areas the City restricted the use of property to buildings "designed for and occupied exclusively by one family."  The ordinance defined "family" as: (a) person living alone, or any of the following groups living together as a single nonprofit housekeeping unit and sharing common living, sleeping, cooking, and eating facilities; (b) any number of people related by blood, marriage, adoption, guardianship or other duly-authorized custodial relationship; (c) three unrelated people; or (d) two unrelated people and any children related to either of them. 

Under this ordinance, landlords were prohibited from renting housing to more than three unrelated persons.  The Ames Rental Property Association (ARPA) sued claiming the ordinance violated equal protection laws, which the lower court dismissed on summary judgment.  On appeal, the Supreme Court of Iowa affirmed the district court stating that the U.S. Supreme Court had previously upheld a more restrictive law under the U.S. Constitution, and that the Ames ordinance was also allowed under the Iowa Constitution. 

The Iowa Supreme Court was not swayed by ARPA's argument that there was no rational relationship between the ordinance and the City's goals of fostering "a sense of community, sanctity of the family, quiet and peaceful neighborhoods, low population, limited congestion of motor vehicles and controlled transiency."  Indeed, the Court cited approving other cases where it was stated that "police power is not confined to the elimination of filth, stench ... [i]t is ample to layout zones where family values, youth values, and the blessings of quiet seclusion and clean air make the area a sanctuary for people."  

This decision provides guidance for cities looking to place more restrictive limits on the living arrangements of its citizens and appears to signal that the Iowa Supreme Court will continue to give great deference to municipal decisions based on an exercise of police power.