I seem to recall a news account describing Armitage's admission to his boss, Secretary Powell, that he had mentioned Plame's role to Novak shortly after the story broke. Why that was held close to the vest I am not sure. An Armitage investigation would yield . . . what? That he admitted to a screw up? He has resigned. Bush can't fire him anymore. Fitzgerald or Wilson himself could have filed charges against Armitage. They didn't, for whatever reason.
Powell could have charged him. He didn't. He too resigned, though I think it was over more substantial issues.
None of that relieves Libby, Rove, or much of anyone else of the responsibility to act with integrity when testifying before a grand jury.
None of that relieves anyone else of the requirement to obey the law, or uphold the law, and basically keep their damned mouths shut about Plame's involvement with the CIA.
DR