At this point give a simple order, provide the information within a week or be fired for insubordination, lose all pension and risk further legal consequences for interfering with matters of national security.
No more games, fire the lot of them if necessary, the harm to do domestically likely outweighs any good they do.
Although I am sympathetic to the goal, methinks firing that lot of vipers all at once would entail some pretty serious blowback, demanding a degree of tactical finesse, poison pills being what they are.