The problem that DOJ prosecutors faced was more fundamental: was the information in Memo 2 classified when Comey gave it to his attorneys? It was undeniably not marked as classified, nor does Comey agree that it was classified. It was designated as classified information only after the fact.
Comey was not an ordinary intelligence employee, and that is where the greatest complication arises. In order to be properly classified under the law, a piece of information has to be designated as such by an "original classification authority" for one of various reasons which are not relevant here. Comey was an original classification authority, meaning that he had the authority to designate something as classified or unclassified on his own initiative. In other words, when he wrote Memo 2 and decided that it contained no classified information, that was an official decision that he had the specific authority to make.
Moreover, Comey was no ordinary original classification authority; he was the FBI Director. As such, his authority flowed from the President through the Attorney General, and more importantly, the authority of the officials who retroactively classified the information flowed through him (or, more accurately, through the FBI Director). This means that, even if one of those officials had wanted to designate this information as classified at the time Comey wrote it, Comey could have overridden the decision, meaning that any decision made by such a subordinate would essentially be futile.
In other words, when Comey wrote Memo 2 and did not classify it, it was not classified. When he gave it to his attorneys, it was not classified. When it was later classified by other FBI officials, that designation did not apply retroactively because it went against the official decision of an original classification authority who was also their senior in the hierarchy. Therefore, Comey could not be charged with mishandling classified information because at the time he allegedly "mishandled" it, it was not classified information. He could not be charged with mishandling unclassified information, because that is not a crime.
In short, the Comey IG report is a perfect case study for a class like Law of Secrecy, because it touches on almost every issue the class covers, and exemplifies the exquisitely intricate ways that all of these topics intertwine with each other.
Kel McClanahan - Executive Director of National Security Counselors, a Washington-area non-profit public interest law firm which specializes in national security law and information and privacy law, and through which he often represents Intelligence Community employees and contractors. He is an adjunct professor at the George Washington University Law School and the American University Washington College of Law, where he teaches various topics in national security law. He sits on the Board of Directors of the National Military Intelligence Foundation, the Board of Directors of the Bar Association of the District of Columbia, and the Steering Committee of the BADC Committee on National Security Law, Policy, and Practice, and is a charter member of the Security Clearance Lawyers Association.
He received his Master of Arts cum laude in Security Studies from the Georgetown University Edmund A. Walsh School of Foreign Service, his Juris Doctorate from the American University Washington College of Law, and his Master of Laws in National Security Law from the Georgetown University Law Center.