793, and 794 for that matter, does not require the information be "classified" only that the information be "connected with national defense" and the release of it could be "used to the injury of the United States or to the advantage of any foreign nation."
Most of the espionage that goes on in the U.S. is culled from open sources. Disparate, unclassified bits of information are collected and assembled to produce useful intelligence. True, it is no secret that the U.S. engages in signals surveillance. But it is to the advantage of the terrorists to have it confirmed, to gain further information about which calls were being monitored, and gain comfort from the furor that has erupted. The feds need to demonstrate that the U.S. was injured by the revelation. They've been loathe to prosecute these cases. This is the perfect opportunity to change that.
Thanks for pointing that out. My typo of "793(a)(3)" should have been "798(a)(3)." 798 does include the word "classified" in the recitation of what constitutes a violation of that section.
793 & 794 recite a list of specific information, much of which can't be kept secret, and as you noted, 793 & 794 do not include the word "classified" in the recitation.
The question I was probing was that of NYT's exposure to criminal charges for publishing. The Pentagon Papers case is in the same vein as the recent publication of the NSA wiretapping allegation, in that regard, and of 793, 794 & 798, 798 seems to be the only section potentially applicable against the NYT.