a conviction for leaking classified info, on the basis of something that "should have been" classified; and similarly, I can't see how the defense could forestall a conviction for leaking classified info, on the basis of something that "should not have been" classified
It was either classified or it was not: if it was not, nobody can sanely argue Mr Manning deliberately released classified info, on the grounds it could have been classified later -- that seems an obvious violation of the ex post facto prohibition, because it would allow prosecution of anybody for any document release, by the simple trick of classifying the material after the release
On the other hand, I suppose it may be germane to the "communicating with the enemy" charge if the video arguably contained combat-operations info that could have been helpful to the enemy, since details of combat-operations might be regarded as deserving automatic protection, whether or not anyone had bothered to formally classify the details
And, honestly, I don't understand why the government picked this high-profile item as part of the complaint. It seems to me that a generation ago, reporters were able to cover such material routinely. All the "embedded reporter" crap we have seen since Vietnam, and all the "embedded reporter" crap we have seen since, is really counterproductive. Two Reuters reporters were killed in this strike, and the Reuters request for the tape should have been honored. And Manning seems not to have been the first to leak this tape: another media outlet reportedly had it prior to the Wikileaks release, but decided not to use it. I'd be happy to see Manning skate on the issue of the tape, or just get a wristslap for it. It's the indiscriminate 750K document dump that concerns me