Actually he does have the authority to decide whether his memo is classified!!! You'd be surprised at how widely that authority is distributed.
The chief use of classification is not what you think, i.e., to protect vital State Secrets. Rather it is to protect confidential private information, to cover-up, to prevent public criticism, prevent embarrassment and indelicate situations in diplomacy, and to prevent interference in your mission by limiting the number of people that have enough access to figure out what you are doing. This doesn't mean the purpose of classification is to cover-up deceit and wrong doing, or mistakes, though it is sometimes used for that, but on the other hand protecting Vital State Secrets is way down on the list of practical reasons classification is used. Every year, there is a staggering number of classified documents, emails, and what not produced by government departments, agencies and sponsored entities, and probably only a small fraction really needs to be classified. The problem is it is easy to get a document or communication classified, but it takes a committee, or worse, to get it unclassified.