All these are major public health problems. In the United States system of government, only states have the right to make laws based on their police power. Police power is used to enact a variety of substantive laws in diverse areas such as zoning, land use, fire and building regulations, gambling, discrimination, parking, crime, licensing professional licensing, alcohol, motor vehicles, bicycles, nuisance, education and sanitation. For example, it is within the police power of a State to enact a law on compulsory vaccination, and the legislature may determine in the first instance whether the best way to protect and prevent the population from smallpox is through vaccination or