Exclusion

Recently, I have been reading "Downtown America: A History of the Place and the People Who Made It" by Alison Isenberg.She claims that one of the earliest conceptions of downtown was as a democratic place that everybody is welcome. All ethnicities, income levels, age groups, cultural groups, etc. could mingle in the downtown. Then the progressive women's movement wanted to clean up the downtown. They restricted access of the undesirables; poor, minorities, youth, were pushed away to make the downtowns nicer, cleaner, more elite places.

I also found this map illustrating some of the methods of exclusion:
The Arsenal of Inclusion & Exclusion

I am not sure that I agree with all of their analysis, but it is certainly a thought provoking piece of work. 

Some Examples:

Animal Zoning Ordinance
Animals have a right to the city too! But most zoning ordinances prohibit animals of the farm variety, declaring them "inharmonious." Inspired in part by the urban agriculture movement, new animal-friendly zoning ordinances such as the one passed by the Cleveland City Council in January, 2009 seek to overturn these restrictions. —Theresa Schwarz

Curfew
Teen curfews are arbitrary and legally-murky. Teen Curfews can be less arbitrary — for example, when Baltimore last year announced a teen curfew in response to a rash of teen stabbings — but many teen curfews represent an unlawful imposition of martial law. In early 2010, San Diego overturned its curfew law due to ambiguous language, and Indianapolis recently overturned its curfew laws when it determined that they forcefully undermine adolescents' first amendment rights. Nonetheless, teen curfews are being implemented in cities and suburbs around the country.

Golf Course

As legal scholar Lior Jacob Strahilevitz points out, a golf course is another type of "exclusionary amenity." Strahilevitz writes that during the 1980s and 1990s, as African Americans began moving to the suburbs in growing numbers, the number of "mandatory membership" residential golf communities in the United States grew significantly. At the time, golf was the most racially segregated warm weather, mass-participation sport in America. (In 1997, 93.4 percent of all American golfers were Caucasian while just 3.1 percent were African American.) Might developers have discovered a method for creating racially-homogeneous communities?