Getting arrested because of hentai

"Matter" means any book, magazine, newspaper, or other printed
or written material, or any picture, drawing, photograph, motion
picture, or other pictorial representation, or any statue or other
figure, or any recording, transcription, or mechanical, chemical, or
electrical reproduction, or any other article, equipment, machine, or
material. "Matter" also means live or recorded telephone messages if
transmitted, disseminated, or distributed as part of a commercial
transaction.

In prosecutions under this chapter, if circumstances of
production, presentation, sale, dissemination, distribution, or
publicity indicate that matter is being commercially exploited by the
defendant for the sake of its prurient appeal, this evidence is
probative with respect to the nature of the matter and may justify
the conclusion that the matter lacks serious literary, artistic,
political, or scientific value.

Canadian laws addressing this are included in the C-46 amended Canadian Criminal Code passed in 1985. It is described under Part V: Sexual Offences, Public Morals and Disordery Conduct: Offences Tending to Corrupt Morals. Section 163.1 defines child pornography to include "a visual representation, whether or not it was made by electronic or mechanical means", that "shows a person who is or is depicted as being under the age of eighteen years and is engaged in or is depicted as engaged in explicit sexual activity", or "the dominant characteristic of which is the depiction, for a sexual purpose, of a sexual organ or the anal region of a person under the age of eighteen years." The definitive Supreme Court of Canada decision, R. v. Sharpe, interprets the statute to include purely fictional material even when no real children were involved in its production.

18 USC 1466A
In response to Ashcroft v. Free Speech Coalition, Congress passed the PROTECT Act of 2003 (also dubbed the Amber Alert Law) and it was signed into law on April 30, 2003 by then president George W. Bush. The law enacted 18 U.S.C. § 1466A, which criminalizes material that has "a visual depiction of any kind, including a drawing, cartoon, sculpture or painting", that "depicts a minor engaging in sexually explicit conduct and is "obscene" or "depicts an image that is, or appears to be, of a minor engaging in ... sexual intercourse ... and lacks serious literary, artistic, political, or scientific value".
By its own terms, the law does not make all simulated child pornography illegal, only that found to be obscene or lacking in serious value. And mere possession of said images is not a violation of the law unless it can be proven that they were transmitted through a common carrier, such as the mail or the internet, or transported across state lines.