Juliette Kayyem and Jane Hamsher both pushed the ball forward on whether Bush's apparent command to reveal classified information was legal. Kayyem points out that declassification has to be in the public interest, and the reference to public interest makes it illogical to assume the "declassification" could be for a single member of the public, Judith Miller. Hamsher highlights the apparent lack of documentation that information was declassified. An update to her post points out that the information was apparently deemed classified afterwards.
While some legal experts say the President has the authority to declassify information at will, that doesn't mean Bush actually declassified the information. For reasons of his own (say, to smear someone without leaving his fingerprints on the smear), Bush may have kept the information classified, but commanded that it be leaked. The apparent fact that it was classified afterwards suggests this is what happened. That would make the disclosure illegal.
The twist I take on Kayyem's post is that if information is declassified to the point where a member of the public (Judith Miller) can have it, then it's completely declassified. Because it apparently was classified afterwards, then Bush didn't declassify it - he illegally leaked.
The only legal way out I can see for Bush is to claim he declassified the information and then at some point after the authorization, but before reporters starting asking for it, he or someone else reclassified it. To use this escape route, they need to claim it and prove it - where's the documentation for the reclassification? And it creates even more political problems for them of using governmental secrets for political advantage, and making Clintonian excuses as to why they didn't break the law. Except in Bush's case, it concerns national security.