The Human Right to Apostate
It is written in the United Nations' Universal Declaration of Human Rights,
http://www.un.org/en/documents/udhr/index.shtml :
Article 18.
Everyone has the right to freedom of thought, conscience and religion; this right includes freedom to change his religion or belief, and freedom, either alone or in community with others and in public or private, to manifest his religion or belief in teaching, practice, worship and observance.
Please note the right to "freedom to change his religion or belief". This is a right for anyone. It doesn't matter if his parents have tried to make him a Christian, a Muslim or a this or that; if his conviction is another, it is his right not to be regarded as Christian or Muslim or whatever.
Please note the the right encompasses not only religion but also belief in general. Secular atheism is included, as well as non-theistic ways of life normally labelled as religions, for example Buddhism.
Please note that it does not include the right to mission, to proselytize, to force others to change their conviction, to respect the conscience of another less than one's own.
Please note that this right does not make the slightest difference between monotheists, polytheists and atheists.
And please not that whoever changes his "religion or belief" will perhaps be hailed as a convert by some, but the convert of some is always the apostate of others.
So apostasy is a basic human right.
According to tradition, both Abraham and Muhammad were brought up in a polytheistic religion but became monotheists; so to the polytheists, Abraham and Muhammed were apostates.
Already because of that, therefore, their followers will not encourage others to follow Abraham's or Muhammad's example if they try to force other people also to be, and to remain, their followers.
At the present point in history, the main culprits in this respect seem to be some Muslims; but Christians have been no better in the past. In my own country, Sweden, it happened as late as 1860 that some ladies were sentenced to forced exile because they had left the Lutheran State Church and converted to Catholicism, thus becoming converts to the Catholics and apostates to the Lutherans.
Shortly afterwards, the laws were changed, but for ninety more years it was possible to leave the state church only if immediately joining another Christian community; which meant that many honest Christians left the church, while every honest atheist had to remain a member...
I am an apostate myself. My parents tried to make me a good Christian, but failed; it turned out my deepest conviction is another, and that's it. To do them justice, they never threatened me in any way.
Other apostates/converts, including some friends of mine, are less lucky.
Be it very clear, however, that any law that forbids someone to leave one religious fold to enter another, or none, is violating this human right, and therefore invalid, regardless in which country it has been passed and which religions or philosophies are concerned.