Cleveland v. United States (1946) upheld the convictions of a
fundamentalist group of polygamous Mormons. Polygamy is not historically
protected by the First Amendment.
In 1890, the Court ruled that Congress could dissolve the Mormon church
because of its practice of polygamy. That action is now considered a clear
violation of the First Amendment.
In Reynolds v. United States (1879), the Supreme Court ruled unanimously
that a federal law prohibiting polygamy did not violate the free exercise
clause of the First Amendment.