The Federation Council is the governing body of the United Federation of Planets. The Council is composed of one representative from each planet, as well as the Federation's head of domestic services, and the head of international relations. Also the UFP President, and one designated Starfleet Representative is included.
Each planet is granted it's own soverign rights, and is entitled to such in all matters dealing with law, policy, etc. However, these rights must be within the Council's guidelines, and the Council ultimately has the final say in such matters where conflict may occur. The council must, at all costs, preserve the independant nature and soverignty of each member planet.