6 GCA § 4205: Laws, Written and Unwritten.

(a) Laws, whether organic or ordinary, are either written or unwritten.

(b) A written law is that which is promulgated in writing, and of which a record is in evidence.

(c) An unwritten law is the law, not promulgated and recorded as mentioned in subsection (b), but which is, nevertheless, observed and administered in the courts of Guam. It has no certain repository, but is collected from the records of the decisions of the courts, and the treatises of learned men.