The age of consent is 16 in DC. It's 18 in Florida, so if he sent even one email from Florida, he's rightfully !@#$ed. But by federal law, it's 16 (Title 19, Section 109A) unless you're soliciting via the internet, in which case it's 18 (HR 4472), and you have to go into the federal sex offenders registry.
The federal law in this case is SO stupid, I can't even begin to explain it. Basically, Foley's violating federal law by emailing the pages, but had he actually molested them...well, that would have been legal, but he still has to admit to the federal government that he commited a crime, even though he didn't. That's probably why the FBI is still "investigating" Foley but hasn't arrested him yet: no one can figure out if what he did was actually a crime or not. The applicable federal law is !@#$ed up beyond belief.