The punishment for apostasy (riddah) is well-known in Islaamic Shareeah. The one who leaves Islaam will be asked to repent by the Shareeah judge in an Islaamic country; if he does not repent and come back to the true religion, he will be killed as a kaafir and apostate, because of the command of the Prophet (peace and blessings of Allaah be upon him): "Whoever changes his religion, kill him." (Reported by al-Bukhaari, 3017).