We have a parallel system for intelligence workers. Twelve out of the first 32 nations that adopted whistle-blower laws had some type of exemption or reduced rights for national security workers. The majority rule is to give them the same protection against retaliation as everyone else.
The structure in our country is that they have free speech rights for dissent within the government agency. They don't have public freedom of expression, but they do have protection against retaliation for operating through the chain of command. They can make disclosures of misconduct, not only through the chain of command but also through the intelligence oversight committees in our Congress.
Actually, that system has been working fairly effectively because the leadership responsible for its enforcement has been operating in good faith and is highly committed to it.