In the United States, the legislative authority granted to local governments varies by state. In some states, known as Home Rule States, an amendment to the state constitution grants cities, municipalities, and/or counties the ability to pass laws to govern themselves as they see fit (so long as they obey the state and federal constitutions). In other states, only limited authority has been granted to local governments by passage of statutes in the state legislature. In these states, a city or county must obtain permission from the state legislature if it wishes to pass a law or ordinance which is not specifically permitted under existing state legislation. Most non-home rule states apply the principle known as Dillon's Rule to determine the bounds of a municipal government's legal authority.