[dragonwriter]

> No congressional district can span more than 1 partial city and/or county.

State legislatures control the definition of administrative subdivisions of the state just as much as they do Congressional districts, so that rule does nothing. A state that is really committed to gerrymandering will just move city and county lines when it redistricts.

A smarter but still corrupt state legislature that wants to gerrymander without disrupting functional local government will make “city” and “county” names of ceremonial subdivisions used for limited purposes, so that redrawing their lines doesn't have much practical effect, and adopt a different set of subdivisions with overlapping lines for most functional local government purposes (“urbanizations” and “parishes”, perhaps.)