I don’t necessarily endorse the writer’s theory, but the piece provides some background that may help those who are unfamiliar with security clearance policies and procedures, especially the applicable Executive Order.
It is common for the unfamiliar to hold all sorts of erroneous notions about classified material. For example, many imagine that classified is synonymous with esoteric or hidden. In fact, classified means exactly what it implies, that the material in question has been judged as belonging to one of three classes of material (confidential, secret, top secret).
Another common mistake is to believe that having, say, a top secret clearance means that you have access to all classes of documents. Not true. In fact, access to any classified document hinges on one’s need to know what it contains. If you have a top secret clearance, you cannot access a confidential document without a need to know. Similarly, even if you have a top secret clearance, you cannot read a top secret document without a need to know what is in it.
Finally, the unfamiliar tend to misunderstand the concept of marking classified material. In particular, marking the material does not in itself make it classified. Classification is performed by a classification authority. The markings merely indicate that a classification authority has reviewed the material and determined the nature of its content. The process here is similar to grading eggs for sale at the supermarket. The eggs themselves are not altered in any way and an ungraded egg may well, on inspection, be found to belong to one of the three graded classifications.
None of these considerations necessarily exonerates Trump from any alleged crimes in holding classified material at Mar A Lago. They do, however, illustrate that the material in question may in fact have been declassified properly, despite any markings the copies bore. As matters currently stand, there is just not enough information available to judge the matter properly. It is not a slam dunk that Trump broke the law.