They don't have to allow you to moonlight, PERIOD. I have no idea what "quasi-federal" agency you're talking about, but they are most likely only limited to what they set as their own policy. If they say that they don't want their police moonlighting as police or security, that's within their rights. There's NOTHING wrong in private or government to treat employees in different jobs differently. Discrimination restrictions only apply to certain protected classes (race, religion, sex, etc...).

