There are many slang terms for the police, and one which has recently been in the news in the UK is "the feds", as in
Cassell's Dictionary of Slang (2005) records this sense as "[1990s+] (UK Black/teen) a policeman". It seems likely that this is a straightforward borrowing from US film and television, where the Feds are agents of the Federal Bureau of Investigation; the UK is not federal and does not have an FBI.
The Royal Air Force police are also called "feds", among other nicknames. This usage is in Partridge's Dictionary of Slang and Unconventional English, 2005 edition, but not in the 1984 edition, nor is it in the 1990 edition of Partridge's A dictionary of RAF slang. In the 2005 dictionary, the RAF usage is dated to 2002, with the note "Adopted from the sense 'a member of the FBI'". As far as I can tell, the nickname is not used elsewhere in the UK armed forces.
Are these two independent borrowings, or has there been some additional influence from one to the other? Are there any other similar slang uses of "feds" in the English-speaking world (referring to police or officials who are not associated with the federal government)?
Update: On reflection, I think that they are probably not related. The point is that the urban "fed" is used for any policeman, whereas the RAF "fed" is only for members of the specific force: it's not used within the RAF for police in general.
My second question – whether there are other (probably ironic) slang uses of "fed" for non-federal police or officials – is still open.