Can you get convicted as a child molestor for having consensual sex with a minor (age 16) when you are age 19?

This is not an uncommon situation and it generates heated argument on both sides of the issue.  However, currently the law is pretty well-settled that new sex offender registry laws can legally be applied to convicted child molesters who have already completed all of the terms of their punishment.  The courts have found that the complying with the registry laws is not additional “punishment”, which would be unconstitutional.  Instead the courts have ruled that the registry laws have a broader purpose of protecting the public and as long as the conditions are not “unreasonable” they are lawful and your friend must comply.  Depending on the state your friend lives in, the conditions can be pretty severe and the penalties for not complying can be serious.  And there are some organizations that are pushing state legislatures to exempt certain  kinds of offenders– like your friend– who may not pose the same risks that the registry laws are trying to guard against.  Your friend would be well-advised to consult an attorney who is experienced in sex offender registry laws and conditions to explore ways to reduce the impact of these laws on him.