FISOs may pass instructions such as clearances on behalf of an authorised person or agency.
Thanks Talkdownman, thats the bit that interests me. Who is authorised? It also says "may" and not "will" or "must"!
If the police walk into an AFISO and say "Instruct that a/c to land" is there a legal obligation on the FISO to pass such instructions on? Whose to say whether such an instruction might have flight safety implications?