"It is difficult to know how to deal with such home grown fanatics."
It's not difficult! Solitary confinement, no access to television or radio, no access to any sort of religious paraphernalia, prison uniform, not their own clothes. Basically make their every waking moment from now until the day they die unbearable!
In a way, life without parole is a more fitting punishment for scum like this, death is to easy a way out for them.