For 150 years the First Amendment restrained only Congress. Between 1940 and 1947 the Supreme Court bound the states to the religion clauses, with Cantwell incorporating free exercise and Everson incorporating non-establishment. Everson enshrined Jefferson's wall of separation while upholding bus fare reimbursement for parochial students, 5-4.
Critics argue the Establishment Clause originally protected state establishments, so incorporating it is conceptually odd. Others dispute whether Black read Jefferson's private letter correctly, and where the child-benefit theory stops is unresolved.



