On a practical basis i cannot evaluate the jurisprudence involved and I would assume the number of people who credibly can is very small, especially in the context of "secret courts for national security reasons".
A useful test would be if any of those few had demonstrated a personal risk using this as a defense and succeeded. The rest of us can only guess the risk based on the reputation of the entites involved.
Remember the constitution only really, effectively, says whatever the current Supreme Court says it means. And really I don't think anyone want's the 100% literal 'shall make no law' interpretation of free speech; that would throw out any kind of labeling laws for starters, companies would have no government compulsion to accurately label drugs or food products for example.