Bob Chilcoat wrote:

"No person may operate a civil aircraft in simulated instrument
flight unless--
(1) The other control seat is occupied by a safety pilot who
possesses at least a private pilot certificate with category and class
ratings appropriate to the aircraft being flown."

Nothing has invalidated his pilot (or CFI) certificate. That's all you
need for 91.109.

HOWEVER 61.3 requires a CURRENT, VALID meidcal for required crew members
which he is at this point. We went around with this and the local FSDO
(and even the FAA HQ) trying so see if there was some "interpretation"
or waiver that could allow my instructor who was in a similar situation
to instruct hooded pilots.