SECTION 8. Foreign flag; display; penalty; exception

Whoever displays the flag or emblem of a foreign country upon the outside of a state, county, city or town building or public schoolhouse shall be punished by a fine of not more than twenty dollars; but, except as to public schoolhouses, this section shall not apply when a citizen of such foreign country becomes the guest of the United States or of the commonwealth, or when a diplomatic representative of a foreign country is a guest at said public building and, if the governor by proclamation authorizes the flag of the country of which such guest is a citizen to be displayed upon public buildings.