That law was not in effect in 2003.
So when FFF was sending those im's, it wasn't illegal.
I don't believe this is true. From this Wikipedia article on the age of consent, it very clearly says the following (there are links on the page itself.)
Federal Laws
{Chapter 117, 18 U.S.C. 2422(b)} forbids the use of the United States Postal Service or other interstate or foreign means of communication, such as telephone calls or use of the internet, to persuade or entice a minor (defined as under 18 throughout chapter) to be involved in a criminal sexual act. The act has to be illegal under state or federal law to be charged with a crime under 2422(b), and can even be applied to situations where both parties are within the same state, but uses an instant messenger program whose servers are in another state.[3]
{Chapter 117, 18 U.S.C. 2423(a)} forbids transporting a minor (defined as under 18) in interstate or foreign commerce with the intent of engaging in criminal sexual acts in which a person can be charged. This subsection is ambigious on its face, and only seems to apply if you transport a minor across state or international lines to a place where the conduct is already illegal to begin with. United States Department of Justice seems to agree with this interpretation.
{Chapter 117, 18 U.S.C. 2423(b)} forbids traveling in interstate or foreign commerce to engage in "illicit sexual conduct" with a minor. 2423(f) refers to Chapter 109A as its bright line for defining "illicit sexual conduct", as for as non-commercial sexual activity is concerned. For the purposes of age of consent, the only provision applicable is {Chapter 109A, 18 U.S.C. 2243(a)}. 2243(a) refers to situations where such younger person is under the age of 16 years, has attained 12 years of age, and the older person is more than 4 years older than the 12-15 year old (persons under 12 are handled under 18 U.S.C. 2241(c) under aggravated sexual abuse). So, the age is 12 years if you're within 4 years of the 12-15 year old's age, 16 under all other circumstances. This most likely reflects Congressional intent to not unduly interfere with a state's age of consent law, which would have been the case if the age was set to 18 under all circumstances. This law is also extraterritorial in nature to US Citizens and Residents who travel outside of the United States.
I have bolded "criminal sexual act" because in various states, the age of consent can be younger than 18. If anyone has a citation that shows that federal law is trumping state AOC laws now, I would really like to see a link to the original federal law.
As I understand it, it's only criminal if actual enticement took place in a state where the AOC was 18 (not 16 or 17 as many states are.) If anyone has any specific knowledge to the contrary, I would really appreciate a link/reference.