9 FAM 42.12 N3.8 If One Spouse Confers Preference Status and the Other Confers Derivative Chargeability
"When one immigrant visa applicant can confer a more favorable preference status upon another at the same time the other immigrant visa applicant can confer a more favorable foreign state chargeability, both applicants can be considered principal aliens. In such cases, however, both applicants must be admitted to the United States simultaneously. The consular officer,
therefore, must issue visas to both applicants simultaneously. For example, if the principal applicant was born in India and the accompanying spouse In France, the principal applicant born in India can be charged to his spouse’s country of chargeability (France), even if the priority date is not current for India."