New York Public Buildings Law Section 141 - Display of foreign flags on public buildings.

 141. Display  of  foreign flags on public buildings. It shall not be
  lawful to display the flag or emblem of any  foreign  country  upon  any
  state,  county  or  municipal building; provided, however, that whenever
  any foreigner shall become the guest of the United States, the state  or
  any  city,  upon  public  proclamation  by the governor or mayor of such
  city, the flag of the country of which such  public  guest  shall  be  a
  citizen may be displayed upon such public buildings.

Last modified: February 3, 2019