Quick Resource: http://wrrc.arizona.edu/sites/wrrc.arizona.edu/files/Quick%20Resouce-%20Policy%20Options%20%28final%29.pdf
Other resources:
Graduate research paper examining implementation options: http://wrrc.arizona.edu/sites/wrrc.arizona.edu/files/Policies%20for%20Implementing%20WH%20in%20Arid%20Regions.pdf
EPA's municipal handbook on rainwater harvesting policies: http://wrrc.arizona.edu/sites/wrrc.arizona.edu/files/EPA_gi_munichandbook_harvesting.pdf