It probably isn’t necessary to point you at something Neil Gaiman has tweeted about, but just in case there are a few of you out there who are not on Twitter, or don’t follow Neil, I’d like to direct you to this press release from the Comic Book Legal Defense Fund.
The actual case in question is about a US citizen who was arrested at the Canadian border on charges of possessing child pornography because he had manga on his laptop. In part this is simply re-hashing old issues. Cartoon sex is not the same as real sex, and in manga all characters tend to look a bit child-like to someone who is not familiar with the art style. However, as the press release notes, this is part of a much wider trend of border guards searching the computers and other portable devices belonging to travelers. Do you know exactly what is on your laptop? Have you checked all of the spam email you get to be sure no pornographic pictures remain?
The main issue here is that border guards are, to a large extent, outside of the law. While you are asking for admission to another country you are neither under their laws nor your own. Eventually this poor American kid will go before a Canadian court, but if the judge throws the case out he will probably have no recourse, and the guards who arrested him will remain free to do the same to other people.