Sex and the law deals with the regulation by law of human sexual activity. Sex laws vary from one place or jurisdiction to another, and have varied over time. Unlawful sexual acts are called sex crimes.
Some laws regarding sexual activity are intended to protect one or all participants, while others are intended to proscribe behavior that has been defined as a crime. For example, a law may proscribe unprotected sex if one person knows that they have a sexual disease or to protect a minor; or it may proscribe non-consensual sex. In general, laws may proscribe acts which are considered either sexual abuse or behavior that societies consider to be inappropriate and against the social norms. Sexual abuse is unwanted sexual contact between two or more adults or two or more minors, and, depending on laws with regard to age of consent, sexual contact between an adult and a minor.
In UK the number of sex offenders within the prison system has been rising rapidly to almost fifth of the total. More sexual offences are being reported (though probably only a fraction of those committed) and the courts are sending convicted offenders to prison for longer periods than earlier. In the USA, between 15 and 22% of the prison population in 1991 were serving sentences for sexual crimes.
In Japan, with a population of 126 million, there are little more than 5,000 complaints of sexual assault a year. However, a 1994 survey of women's groups found that 71% of women said they had been sexually molested. The frequent incidence reported was of groping, usually on overcrowded trains.