Any act that is forbidden in an individual's religion does not make the act illegal..
If a country put out a law that says having a child out of wedlock is illegal then it is illegal... if they don't have a law that is against it, then it legal... Most countries has a law protecting this children to make sure that their parents supports them on their needs
Any sex act that you do in the privacy of your home (in most countries) is no concern of anyone or the government but if you do the same act in public then it becomes their concern..
Majority of the Islam countries has a law against having sexbefore marriage, children out of wedlock and opposite sex living together.. then that makes it illegal..
So it depends on where you are, if an act is condoned or not and if it illegal or not..