Something that is not mentioned as often as it should:
As noted in a 2008 report by a Christian human-rights organization, “Apostates from Islam to another religion suffer a host of serious abuses from their families, communities and nations.” These renegade Muslims may well face the death penalty in countries such as Saudi Arabia, Iran, and Sudan, and other forms of oppression in many other Muslim societies.
The reason for this systemic violation of religious freedom is, unfortunately, religious. Most classical schools of sharia law consider apostasy from Islam a crime punishable by death. A hadith attributed to the Prophet Muhammad is quite clear on this: “If somebody [among Muslims] discards his religion, kill him.” The implication is that Islam is a religion with free entry but no free exit.
For this reason, some Muslim countries have had difficulty accepting the Universal Declaration of Human Rights (UDHR) adopted by the U.N. General Assembly in 1948. Among its provisions is the “freedom to change [one's] religion or belief.” Spokesmen for Saudi Arabia, in particular, have consistently opposed this clause, noting that it “might be interpreted as giving missionaries and proselytizers a free rein.”
As an alternative to this “free rein,” the Organization of the Islamic Conference (OIC), of which all Muslim-majority states are members, adopted in 1990 a Universal Declaration of Human Rights (UDHR) in Islam. It denounced efforts “to exploit [one's] poverty or ignorance in order to convert him to another religion, or to atheism.” Deserting Islam was not welcome, nor was calling for its desertion.
The disparity between the UDHR and the “Islamic” version still exists, and this thorny issue of apostasy is the biggest obstacle to resolution. It even has led some conservative Muslims to condemn the UDHR as evil. Grand Ayatollah Khamenei, the supreme leader of the Islamic Republic of Iran, for example, denounced it as “mumbo jumbo by disciples of Satan.” He explained his reasoning explicitly: “When we want to find out what is right and what is wrong, we do not go to the United Nations, we go to the Holy Koran.”