Where to find information on how to establish a domicile in US that's accepted by USCIS?

Question

A family member who has US citizenship wants to sponsor her husband, but she didn't live in USA for many years.
How can she re-establish herself there? And how to prove it? What are the necessary documents? Where to find information other than uscis.gov site?
She went to the consular but received no help at all.

Answer 1

You may be an American citizen anywhere in the world.

However, what you are asking for is probably ILLEGAL. That's why the consulate won't help her. Neither will I.