Given that disruption of regular services is the most potent weapon in any union's arsenal, what kind of leverage do federal workers' unions really have?
Edit: It appears a mass "sickout" is a possible way to circumvent the legal definition of a "strike" to cause work stoppage:
A "sickout", or (especially by uniformed police officers) "blue flu", is a type of strike action in which the strikers call in sick. This is used in cases where laws prohibit certain employees from declaring a strike. Police, firefighters, air traffic controllers, and teachers in some U.S. states are among the groups commonly barred from striking usually by state and federal laws meant to ensure the safety or security of the general public.