The crux

Obama says:

We must not protect information merely because it reveals the violation of a law or embarrasses the government.

And he also says this:

In short, there is a clear and compelling reason to not release these particular photos. There are nearly 200,000 Americans who are serving in harm's way, and I have a solemn responsibility for their safety as Commander-in-Chief. Nothing would be gained by the release of these photos that matters more than the lives of our young men and women serving in harm's way.

So the basic principle that Obama outlines is: if releasing information will endanger "the lives of our young men and women serving in harm's way", then it should not be released--even if the information reveals government law breaking.

But this seems perverse to me. If you allow the executive branch to evade accountability by claiming that evidence released will endanger the troops, then the executive branch will simply cook up various rationales to justify the protection of damning evidence. What you need is an outside authority determining if the threat described by the executive branch is 1) legit and 2) of sufficient severity to offset the public interest in holding the executive branch accountable for its actions. It's not clear to me that Obama lays out such a mechanism.

Moreover: what if the release of information really will endanger the troops, and also reveals serious law breaking? Do these laws simply go unpunished? Is there some mechanism for seeking justice "behind closed doors"? Or does law breaking that falls into this category receive a free pass?