Legal Question in Constitutional Law in California

The First Amendment to the U.S. Constitution protects your right to view a very wide variety of material, but "obscene" matter is not protected by the First Amendment. That said, something can be highly offensive to nearly everyone (except possibly you) and still not qualify as "obscene." To qualify as "obscene" a work must appeal solely to prurient interest and be utterly lacking in redeeming social value such as literary, artistic, scientific or cultural value, based on local community standards. "Snuff" films, child porn, and depictions of cruelty to humans and animals would be good examples (having child porn on your computer is a good way to earn a long stretch in federal prison). However, "obscenity" is a very difficult test to meet, at least in California. I doubt that you could or would be prosecuted for viewing or possessing nearly all sexually oriented material depicting consenting adults. Obscenity prosecutions are more likely in Southern or Midwestern states, and they are more likely to be initiated by Republican prosecutors. If you are using a P2P or torrent to obtain this material, be aware that you are also uploading and distributing the material to the whole world at the same time you are downloading it. This could well get you in trouble in some other, faraway, jurisdiction. Obscenity law is complicated, and this answer is neither intended to be authoritative nor is it based on legal research. Please Get Professional Help.

Mr. Stone gives a good and comprehensive answer. I write separately just to clarify one point. You seem to be under the impression that there is some single law of obscenity. That is absolutely not the case. There are state and federal laws governing illegal conduct that may or may not also be obscene, such as child porn. Pictures of naked boys are not all obscene, per se, but if they're not your family photos, or sent by friends for purely innocent purposes, it is highly illegal to posess them. That law exists for reasons having to do with protection of children, not due to obscenity. There are, however, no universal laws of obscenity. They are all local or state-wide, and of course other countries have their own laws, but there is no national prohibition on distribution or transportation of obscene material. There are also laws dealing with obscenity only in specific contexts, for example in Ohio it is illegal to provide obscene materials to a minor, but not adults. And there are regulations prohibiting obscene materials in television, for example.

Mr. Stone and Mr. McCormick have both given you very good answers. I have just one point to add.

Obscenity prosecutions are extremely rare in California. When they occur, the defendant is almost always someone who has displayed or distributed the allegedly obscene material, not someone who merely enjoyed looking at it -- especially in the privacy of his own home. I don't know if anyone has been prosecuted recently in this state just for looking at such material.