There has been significant discussion over the past week about potential consequences of downloading and sharing WikiLeaks documents classified by the U.S. government, ranging from schools' cautions to their students about potential job consequences to government agencies restricting access or discussion. One thing missing from most of this discussion is the relevant law. It does not seem to be widely understood that the public exposure of these documents does NOT declassify them. WikiLeaks can disclose classified information, but it cannot declassify it. As a matter of law these documents retain the original classification assigned to them until such time as an executive branch official with legal authority to alter the classification formally does so, or until the period of time established for them to remain classified has expired. (Many classified documents will be marked with a specified duration for their classification). While it may seem like government agencies endeavoring to limit access to the WikiLeaks site or public discussion of the documents by their employees are engaging in politically motivated censorship, it is in fact consistent with their obligations to enforce the law.
The reason that the fact that these documents continue to be classified really matters is federal espionage law, particularly 18 U.S.C. sec. 793. Most subsections of that statute contain a mens rea requirement that the perpetrator intends or has reason to believe that the information they are accessing or distributing "is to be used to the injury of the United States." I would contend that a citizen accessing information online for the purpose of informing themselves about what the U.S. government has been doing does not satisfy this requirement and could not reasonably be prosecuted under those sections. It is not hard to see, however, that those responsible for leaking the information to WikiLeaks, and potentially those responsible for posting it--knowing it would almost certainly be accessed by foreign governments and groups with interests inimical to those of the U.S. might reasonably be prosecuted under these sections. But the way U.S. espionage law currently reads, any American who simply retains or forwards any of these documents could also find them self violating federal law.