The Religious Land Use and Institutionalized Persons Act (2000, RLUIPA) prohibited government from imposing a substantial burden on prisoners' religious exercise, unless the burden furthered a "compelling government interest." Prisoners in Ohio alleged in federal district court that prison officials violated RLUIPA by failing to accomodate the inmates' exercise of their "nonmainstream" religions. The prison officials argued that the act improperly advanced religion and thus violated the First Amendment's establishment clause (which prohibited government from making laws "respecting an establishment of religion"). The district court rejected that argument and ruled for the inmates. The Sixth Circuit Court of Appeals reversed.
https://www.oyez.org/cases/2004/03-9877