An important detail in the US juristiction certainly. On a practical basis i cannot evaluate the jurisprudence involved and I would assume the number of people

An important detail in the US juristiction certainly. 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.