What If They Levitate & Their Heads Spin?

The Supremes unanimously upheld the rights of Satanists & witches to practice their religion within State prisons yesterday. The case seems to have been rightly decided, but it points to a weakness in our doctrine of freedom of religion, no? RC2 supposes that most "Satanists" are just having fun at the State's expense. But what if they take it seriously and become possessed?
Don't laugh, I'm just asking as a thought experiment. Does our political system have any means of defending itself against Satanism?

(By the way, In Legion, a sequel to the Exorcist, the demon resides in the soul of a serial killer sentenced to life in prison. The demon conveniently leaps into other souls at night and walks around freely committing mayhem, only to return to his host soul in prison by morning.)