The Supreme Court has unanimously upheld Section 3 of the Religious Land Use and Institutionalized Persons Act, which provides in pertinent part:
No government shall impose a substantial burden on the religious exercise of a person residing in or confined to [a penal] institution,? unless the burden furthers ?a compelling governmental interest,? and does so by ?the least restrictive means.?
Perhaps the most interesting aspect fo the opinion is Justice Thomas' concurrence, in which he explains why the Act does not offend his federalism-based understanding of the First Amendment's religion clauses. Thomas believes that the First Amendment's Establishment Clause does not erect a wall of separation between church and state, but rather was simply designed to prevent Congress from intefering in state establishments of religion. In his concurrence, Thomas explains why the Congress can nevertheless require states to show a compelling reason for restricting religious exercises by inmates:
Even when enacting laws that bind the States pursuant to valid exercises of its enumerated powers, Congress need not observe strict separation between church and state, or steer clear of the subject of religion. It need only refrain from making laws ?respecting an establishment of religion?; it must not interfere with a state establishment of religion. For example, Congress presumably could not require a State to establish a religion any more than it could preclude a State from establishing a religion.
Based on what I've read of the relevant history, I've come to believe that Thomas' interpretation of the Establishment Clause is correct. The extension of that clause into the so-called wall of separation is a modern invention foisted on us by the Court based mostly on the writings and wishes of Thomas Jefferson, who was in France during the relevant time period. Thomas' explanation of how the proper understanding of the Establishment Clause relates to the limits of Congressional power with respect to religion thus is a very important step forward in the development of a proper understanding fo the Clause as a whole.