Good question, overstress . I also feel I should know the answer, but don't.
Tried the ICAO website - no help. All I can offer to the debate is the para at the Intro to AICs, which is entitled "Status".
That says, "AICs are originated whenever it is necessary to promulgate information which does not qualify.....for inclusion in the AIP, or promulgation by supplement".
The fact that it does not refer to any legal status tends to support OzExpat 's remarks.