This observation is mostly stolen from:
http://glenngreenwald.blogspot.com/2006/09/gop-house-leadership-and-mark-foley.htmlIn D.C., the age of consent is 16 years old. This means that once a person has attained the age of 16, they can have sexual intercourse with someone of any age. Thus, strangely, it would have been legally acceptable (let me emphasize
legally; I think it's a pretty clear case that it would not be morally acceptable) for Foley to go to a D.C. high school and pick out a senior to have a sexual relationoship with.
However, Foley did likely break federal law. Under the Adam Walsh Child Protection and Safety Act of 2006, any discussion or solicitation of sexual acts over the Internet would be illegal. Furthermore, as I understand the law, any pictures that a 16 year old would have sent Foley would be child pornography, opening up a whole additional can of worms.
So, the public policy our legal system seems to be enforcing is this: You can have sex with a 16 year old, just don't talk about it over the Internet, and don't take dirty pictures.
(As an aside to address some posts I see coming, based on past experience: Foley's actions were morally reprehensible, as he abused his position as a Congressperson to sexually harass former employees who were at a severe power disadvantage. It shouldn't need to be said, but this post should not be read as justifying his actions. I'm glad Foley was removed from the House, and from what we know so far, the leadership is almost as culpable as he is for covering it up).