Islamic Religious Authority
....There is no official authority who decides whether a person is accepted to, or dismissed from, the community of believers, known as the Ummah ("Family"). Islam is open to all, regardless of race, age, gender, or previous beliefs. It is enough to believe in the central beliefs of Islam. This is formally done by reciting the shahada, the statement of belief of Islam, without which a person cannot be classed a Muslim. It is enough to believe and say that you are a Muslim, and behave in a manner befitting a Muslim to be accepted into the community of Islam.