Key references: Article 134, UCMJ; U.S. NAVY REGULATIONS 1165 (applies to both Navy and Marine Corps); OPNAVINST 5370.2C (applies only to Navy); Marine Corps Manual 1100.4 (applies only to MC).
Background: The U.S. Navy has historically relied upon custom and tradition to define the bounds of acceptable personal relationships among its members and unduly familiar relationships between officers and enlisted members have traditionally been contrary to Naval custom, because they undermine the respect for authority.
Definition: Generally, fraternization is an unduly familiar personal relationship between an officer member and an enlisted member that does not respect the difference in rank or grade. Relationships between officer members and between enlisted members that are prejudicial to good order and discipline or of a nature to bring discredit on the Naval service are unduly familiar and also constitute fraternization.
Article 134, UCMJ: The accused was a Commissioned or Warrant Officer; the accused fraternized with an enlisted member; the accused knew the person was an enlisted member; the fraternization violated the traditions and customs of the accused’s service; and the conduct was prejudicial to good order and discipline or was of a nature to bring discredit on the armed services. Although still a valid standard, its applicability is limited since it requires the accused to be an officer, the other person to be an enlisted member, and the conduct was prejudicial to good order and discipline of the service
OPNAVINST 5370.2B (the preferred rule): Prohibits unduly familiar relationships between officer and enlisted personnel that do not respect the differences in grade or rank (nearly identical language as U.S. NAVY REGULATIONS 1165). It is also a General Order and punishable under Article 92, UCMJ. Relationships covered by this Instruction include unduly familiar relationships between officers...