18 U.S.C. § 611: Voting by aliens

the election is held partly for some other purpose; aliens are authorized to vote for such other purpose under a State constitution or statute or a local ordinance; and voting for such other purpose is conducted independently of voting for a candidate for such Federal offices, in such a manner that an alien has the opportunity to vote for such other purpose, but not an opportunity to vote for a candidate for any one or more of such Federal offices. Any person who violates this section shall be fined under this title, imprisoned not more than one year, or both. each natural parent of the alien (or, in the case of an adopted alien, each adoptive parent of the alien) is or was a citizen (whether by birth or naturalization); the alien permanently resided in the United States prior to attaining the age of 16; and the alien reasonably believed at the time of voting in violation of such subsection that he or she was a citizen of the United States.