I think the entire corpus of classified (classified by the governement as secret, etc.) falls into that category. Much of this material is too detailed for encyclopedic purposes, but much would be encyclopedic if we knew it or were free to publish it.
More or less along the same line, considering the national security needs of the United States with respect to the "War on Terror", certain photographs and information, for example regarding the details of security precautions and certain nifty destructive techniques might fall into this category.
Fred
From: "Jimmy (Jimbo) Wales" jwales@wikia.com Reply-To: English Wikipedia wikien-l@Wikipedia.org Date: Wed, 4 Aug 2004 09:28:45 -0700 To: English Wikipedia wikien-l@Wikipedia.org Subject: Re: [WikiEN-l] British copyright law != American copyright law
p.s. I would be interested in gathering examples of content that (a) we ought to have in the encyclopedia on editorial grounds but that (b) would not be legal for us to host in the United States.
To my knowledge, virtually all examples of content that is not legal in the U.S., but which *is* legal elsewhere, are not really relevant to our encyclopedic mission. The age of consent for models in pornographic pictures in the U.S. is 18 in the U.S., but lower in some other countries, but we don't publish pornographic pictures so this is irrelevant to us.