Treason. Period.
Leftists have been publishing classified information since I was in college, all for a "higher purpose," of course. Don't see a lot of them doing prison time. Philip Agee and Daniel Ellsberg are heroes of the Left, regardless of the death and damage they caused (at least one agent was killed due to Agee's actions. As far as I know, Plame is still doing photo shoots). Agee, not surprisingly, seems to be currently running a travel agency to communist Cuba.
As always, the legality and morality of an action seems to largely depend on whose agenda is being served.