N.J. Stat. § 52:3-4
It shall be unlawful to display the flag or emblem of any foreign state or country either on public or private property within this state, unless such foreign flag or emblem be accompanied by a national flag of the United States of America, of at least equal dimensions; but whenever a foreigner becomes the guest of the United States, the state, or any city or municipality, upon the proclamation of the governor or the mayor of any such city or municipality, the flag of the country of which such public guest shall be a citizen may be displayed upon any state, county or municipal building without being accompanied by a national flag as above provided.
Any person violating this section shall be guilty of a misdemeanor, and punished by a fine not exceeding one hundred dollars, or imprisonment in the county jail not exceeding sixty days, or both.
N.J.S. § 52:3-4