Anderson v. Liard. Here is a brief summary of this case taken from "God, Caesar and the Constitution" by Dr. Leo Pfeffer. The entire text of the court's opinion can be found in any university law library and is cited as 466 F.2d 283 (1972).
Warner v. Orange County Department of Probation. Full text of the 1996 Second Circuit Court of Appeals opinion holding that a person's mandatory attendance at Alcoholics Anonymous meetings violates the Establishment Clause of the U.S. Constitution because of the AA program's religious nature.
Kerr v. Farrey. Full text of the 1996 Seventh Circuit Court of Appeals opinion holding that Narcotics Anonymous is a religious program and that a prisoner cannot be forced to attend NA without violating the Establishment Clause.
Evans v. Tennessee Board of Paroles. Full text of the Nov. 1997 Tennessee Supreme Court opinion holding that a prisoner may not be required to attend Alcoholics Anonymous as a condition of parole insofar as AA is a religious program within the meaning of the First Amendment and no alternative secular program is available to him.
Griffin v. Coughlin. Full text of the 1996 New York Court of Appeals opinion upholding the right of a prisoner to attend a secular alternative to AA on the ground that mandatory attendance at AA violates the constitutional separation of church and state.
This will take you to all the Supreme Court opinions on the Religion Clauses of the Constitution.