1. Material which violates United States law
Our servers are located in the United States, and so that means that LiveJournal is subject to United States law. This particular item in our policy covers content that inherently violates specific United States criminal statutes. (That is, the material itself is against the law.)
This includes threats of physical harm against the President or other executive officers, child pornography (photos or videos), or other material -- including drawings and text -- that explicitly depicts minors under the age of 18 (real or not) in a graphic sexual context. Or, in other words: Romeo and Juliet is okay. Teens talking about their experiences with sex is okay. Smut focused on a twelve year old is not okay.
These laws aren't unique to LiveJournal or even the Internet -- all media and publications in the United States are subject to them, and so we need to make sure that stuff on LJ doesn't violate these laws.
When asked to cite U.S. criminal statutes that forbid underage fictional smut, the OP either does not reply or handwaves elaborately with passive-aggressive smileys and references to "obscenity laws". What the fuck?
Comments off because if you feel strongly about any of this, I want you to tell LJ, not me.