Under the new law, a child born outside of the United States acquires automatic citizenship under INA 320, even if the child is residing outside the United States, in cases where the child is a lawful permanent resident (LPR) and is in the legal and physical custody of his or her U.S. citizen parent who is:
• Stationed and residing outside of the United States as a member of the U.S. armed forces; 
• Stationed and residing outside of the United States as an employee of the U.S. government; or
• The spouse residing outside the United States in marital union with a U.S. armed forces member or U.S. government employee who is stationed outside of the United States.

The policy manual update is here.