In Britain, the legislation requires that consent must not have been given by the potential victim for the crime of rape to have been committed - though there is apparently some room for the other party here in that if the potential perpetrator 'reasonably' believes that the potential victim has consented then technically rape has not occurred.
In the case of this post and John Wedger, however, we are talking about children who - in the legislation - are unable to consent to sex before the age of 16 - so all sex, in that sense, is criminal.