That's kind of a hard question to answer, honestly. In theory it's just actual CP, but there have been instances of overzealous law enforcement agencies prosecuting people for drawings (like hentai stuff) on the theory that they could have used living child models to create the images. If the courts do their jobs right those should never get convictions unless they can actually prove that that is what really happened. As far as real people are concerned as long as the actor/actress is over 18 then you're golden, regardless of how young the character is.
*Edit* - And as far as people getting crazy about "freedom" I'm inclined to agree, but with freedom of expression specifically it's protected in amendment number 1 of the constitution. There's no constitutional provision protecting your right to not wear a helmet.
*Edit 2* -
So it's not actually illegal to sell/possess it? In what sense is that kind of stuff banned then?