Green’s Dictionary of Slang

(US) involvement in a court case or similar legal situation.

1982–2004		G. Sculatti Catalog of Cool 🌐 Sue City (descriptive phrase): Involved in a court action or otherwise engaged in legal matters.
2003		Chicago Sun-Times 16 Nov. 🌐 Sibling rivalry came into play, though not quite sibling riflery. It was never Sue City, but not exactly Coo City.