N.D. Cent. Code § 37-07-01

Any person who is a citizen of the United States, or who has declared the person's intention to become a citizen, if within the ages set forth in the National Defense Act of 1920, as amended, able-bodied, free from disease, of good character, and of temperate habits, may be originally enlisted in the national guard of this state under the restrictions contained in this title for a term of not less than three years and as provided by national guard regulations promulgated by the secretary of defense.