The states cannot interfere with the free exercise of religion. Decided May 20, 1940 (argued March 29, 1940). Opinion of the Court: Owen Roberts → go there Applied: the First Amendment → go there Applied: the Fourteenth Amendment → go there Topic: Freedom of religion. Cantwell v. Connecticut, 310 U.S. 296 (1940), is a landmark court decision by the United States Supreme Court holding that the First Amendment's federal protection of religious free exercise incorporates via the Due Process Clause of the Fourteenth Amendment and so applies to state governments too. Wiki link