??? Zoning is the mechanism to disallow infill, it can't come in response to it. The book "The Color of Law" by Richard Rothstein covers how zoning as used as a new tool for racial exclusion in its third chapter. Indeed, modern socal remains a highly segregated area thanks to zoning decisions that ensure working class people, who are predominantly nonwhite, will find no suitable housing they might afford in the various lily white strongholds.