Mary Dogood, a member of the school board in ABC County, is appalled at the amount of junk food in the schools. She convinces the state legislature to pass an ordinance that no stores may sell any unhealthy junk food within 500 feet of any school or day care center. A teacher of political science raises the issue of whether the regulation is valid and is told that it is a valid exercise of the jurisdiction's police power to protect its citizens. Convenience stores balk at the regulation and challenge it in court. What concept is addressed regarding the reference to "police power"