The United States Supreme Court has entered decisively into a new fourth era of American religious freedom. In the first era, from 1776 to 1940, the Court largely left governance of religious freedom to the individual states and did little to enforce the First Amendment religion clauses. In the second era, from 1940 to 1990, the Court "incorporated" the First Amendment into the Fourteenth Amendment Due Process Clause and applied both a strong Free Exercise Clause and a strong Establishment Clause against federal, state and local governments alike, most paradigmatically through cases such as Sherbert v. Verner and Lemon v. Kurtzman. In the third era, from the mid-1980s to 2010, the Court softened the review available under both religion clauses allowing neutral laws of general applicability to pass First Amendment challenges, even if they heavily burdened religion. But since the early 2010s, while the Court has maintained a weaker Establishment Clause, it has strengthened the grip of the Free Exercise Clause, the Free Speech Clause, and federal statutes applied to religion. These moves have shrunk the range of government activity prohibited by the Establishment Clause but expanded the areas of religious activity protected by the Free Exercise and Free Speech Clauses.
Witte, Jr., John (Sun,) studied this question.