Via Translating Jihad:

“(Third), the one who abandons his religion, and separates himself from the community.” The hadith is in both of the Sahihs (i.e. Bukhari and Muslim). “The one who abandons his religion, and separates himself from the community.” Islam does not compel anyone to enter it. This (concept) needs to be firmly established. Islam does not compel anyone to enter it. No. There is no compulsion in religion. But rather we preach (Islam) in truth, mercy, propriety, and humility. Whoever says after the preaching — whoever says after (receiving) the preaching and the call (to Islam), “No, I will not enter this religion.” We say to him, “There is no compulsion in religion.” Truth stands out clear from error. We recite the saying of Almighty Allah, “Let him who will believe, and let him who will disbelieve” (Qur’an 18:29). We recite the saying of Allah Almighty, “You have your religion and I have my religion” (Qur’an 109:6). Beautiful. This is after the preaching and the call (to Islam).

But if he enters Islam of his own free will and choice, he does not have the right to leave the religion of Allah whenever he wants, to shake the foundations of Muslim society. No, he does not have the right. Absolutely not. But he does have the right, after having (Islam) preached to him, to say, “I will enter” or “I will not enter this religion.” But to enter it just to leave it whenever he wants? No. This is something which is unacceptable in the religion of Almighty Allah. Show me a constitution anywhere on earth which grants this for its citizens. But rather whoever comes out against the constitution of any nation is accused of treason. Everyone familiar with treason knows that the penalty is death. So what do you think about the one who betrays the religion of Allah Almighty, the one who betrays Allah and His Messenger? “O ye who believe! Do not betray Allah and His Messenger, nor knowingly betray your trusts”