Green’s Dictionary of Slang

City Hall n.

In phrases

you can’t fight City Hall (also go fight City Hall)

(US) you can’t win against the establishment.

[US]A. Kober My Dear Bella 63: Mr. Gross looked at his wife and shrugged his shoulders in a gesture of helplessness. ‘Nu go fight City Hall!’.
[US]E. Rosenberg [bk title] Go Fight City Hall.
[US]Chopper Mag. Jan. 60/2: You can’t fight the man, City Hall, and Johnny Joe Citizen.