'The Bill of Rights, First Amendment to the United States Constitution, passed in 1789 includes the Free Excercise Clause which guarantees the freedom of religion. :

Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the government for a redress of grievances.