... if only for the purposes of the First Amendment.
A Wisconsin inmate wins in the 7th Circuit today, after prison authorities denied him the ability to form an in-house atheist study group:
Kaufman v. McCaughtry
The discussion takes place on pages two through eight.* It cites a lot of cases, but is mostly a non-technical discourse on what atheism is, in particular as it applies to religious freedom in the U.S. (or at in least Wisconsin, Illinois, and Indiana, the 7th Circuit's jurisdiction).
* Interested readers may wish to continue on to the court's brief engagement with the matter of the plaintiff's gay S&M porn.