DescentBB

The Islamic law code says this about freedom of religion:

Leaving Islam is the ugliest form of unbelief (kufr) and the worst. It may come about through sarcasm, as when someone is told, "Trim your nails, it is sunna," and he replies, "I would not do it even if it were," as opposed to when some circumstance exists which exonerates him of having committed apostasy, such as when his tongue runs away with him, or when he is quoting someone, or says it out of fear.
When a person who has reached puberty and is sane voluntarily apostasizes from Islam, he deserves to be killed.

In such a case, it is obligatory for the caliph (or his representative) to ask him to repent and return to Islam. If he does, it is accepted from him, but if he refuses, he is immediately killed.