Immigration and Nationality Act [INA 202 (b)(2)]
Rules for Chargeability: if an alien is chargeable to a different foreign
state from that of his spouse, the foreign state to which such alien is
chargeable may, if necessary to prevent the separation of husband and wife,
be determined by the foreign state of the spouse he is accompanying or
following to join, if such spouse has received or would be qualified for an
immigrant visa and if immigration charged to the foreign state to which such
spouse has been or would be chargeable has not reached a numerical level
established for that fiscal year;