Green’s Dictionary of Slang

1. (Aus. Und., also raise the flag) to appeal to a higher court.

1975		Bulletin (Sydney) 26 Apr. 44: ‘What about flyin’ the flag, mate?’ ‘No way in the world I won’t.’.
1990		Tupper & Wortley Aus. Prison Sl. Gloss. 🌐 Flag. As in ‘to raise the flag’, ie to appeal one’s sentence.

2. to make a fuss for form’s sake.

1993

M.B. ‘Chopper’ Read How to Shoot Friends 24: I think they all knew another book was in the wind and they were only flying the flag.