3 GCA § 9118: Grounds for Challenge.

A person present to vote may be orally challenged by any voter of the same precinct upon any or all of the following grounds:

(a) that he or she is not the person whose name appears on the register;

(b) that he or she is not a resident of Guam;

(c) that he or she is not a citizen of the United States;

(d) that he or she is not a resident of the precinct at which he or she is voting;

(e) that he or she has voted that day;

(f) that he or she voted in another precinct; and

(g) that he or she voted in another U.S. jurisdiction.