Hi Joan,
I copied a portion from the following website below. Not sure if it helps, but it does appear he needs a reentry permit. Good luck!
http://www.immigrationsolution...tion-forms/N-470.pdf"To obtain approval to preserve residency, such permanent residents must file a Form N-470 application before departing from the United States.
The regulations are different for religious workers proceeding abroad to perform religious duties. Religious workers may apply before or after departure, or after return to the UnitedStates. They are not required to have lived in the United States for a specific period of time prior to filing Form N-470.
Filing a Form N-470 does not relieve a permanent resident from obtaining a reentry permit, in advance of trips outside the United States for a year or more, nor does it relieve the applicant from the naturalization law's physical presence requirement.
An applicant qualifying for the residency preservation may extend the benefit to his or her spouse and dependent children who are all members of the same household and have lived with the principal applicant while abroad".
Do not go where the path may lead, go instead where there is no path and leave a trail.
(Ralph Waldo Emerson)