We have different ages of consent for sex, but there's a categorical limit of 18 for posing for pornography.

It's caused some interesting court cases such as one in Utah where a scumbag had sex with a girl. He also took pictures of it. When it ended up in court he was arguing how can the sex be legal but to take a picture of it (they were not published) not be? (The prosecution was trying to throw the book at him since the blackmail charge wasn't enough to make them happy.) We moved before I found out how it came out.