The following are excerpts from an interview with Saudi cleric Said Al-Qahtani:
Host: Those who consider a certain person to be a heretic, whom it is permitted to kill – Who has the authority to carry out the punishment? We say that the youth must understand that even if we proclaim somebody to be a heretic, it's the ruler's right, not yours, to carry out his punishment. Right?
Al-Qahtani: Yes. First of all, making the verdict. Proclaiming someone a heretic is a religious ruling that only religious judges are allowed to sign. Just like chopping off hands. Allah says in the Koran: "Cut off the hands of thieves, male and female". This is a religious law, but do we cut off the hand of anybody see stealing? This would turn life into anarchy and barbarism. Only a judge can rule that a hand be chopped off, after the conditions for chopping off hands have been met and the restrictions are found not to apply, because there are many conditions and restrictions. If the conditions are met and the restrictions do not apply, the chopping off is allowed. But who makes the ruling? The religious judge. And who carries it out? It is carried out by the (political) ruler. The same goes for proclaiming heresy. It is a religious decision, that can be made only by a judge. Whoever has committed an heretic or has uttered heretic words is brought in and the judge confirms that the two conditions of heresy are met, and that the four restrictions do not apply. Then, the judge sentences this heretic, whose heresy has been confirmed and the ruler carries out Allah's law. The judge also determines who will carry out the punishment.
Host: Does he also define who will carry out the punishment?
Al-Qahtani: Yes. While in a state of anarchy, I appoint myself judge and ruler and start killing people. In what religion does this happen?!