While Freedom of Religion is a vital clause in the United States Constitution, the government has often prevented minority groups from practicing their religions.
Native Americans were constrained to reservations for a long time, and only allowed to practice their religions on reservation land. Since reservation land was technically not U.S. land but "sovereign nations," state and local government could restrain Native American religion off-site, claiming that they were technically not U.S. citizens and so did not have protection under the constitution.
Native American rights were considered unimportant throughout most of the 1700s and 1800s, as the fledgling U.S. found its place in the world and fought foreign and domestic threats. U.S. soldiers occupied the reservations, arbitrarily imposing U.S. laws while preventing Native Americans from practicing their traditions, on or off reservation. Finally, in the 1978 American Indian Religious Freedom Act, the U.S. government formally recognized the Native American right to religion, allowing practice outside reservations and preventing government from influencing or threatening their rights.