Green card holder's extended India stay

[rarer3]

Hi,
My father in law is a green card holder. He went to India to take care of his mother, but will be required to stay about a year it appears. Is there a 6 month limit? What happens if he crosses that limit (with good reason we feel)? What can we do?
Please help.

[kevinkallis]

He can apply for a returning visa (SB-1) at the U.S. Embassy or Consulate where he is currently staying