The most common[source?] kind of child abduction is when parents take their children, in what is also called parental child abduction. In 2010, that happened 200,000 times in the United States. This often happens when a marriage breaks up.
The exact legal situation is very complex, and varies between countries. All countries have laws defining legal adulthood, and most have laws about age of sexual maturity (age when young people may decide for themselves about their sexual activities with other people), and laws about drinking alcohol and other activities. Also, there are usually laws about abduction or kidnapping by strangers (people unknown to the child).