1937. (2523) No Additional Grounds. No grounding connection shall be made to the grounded conductor of an interior wiring system on the load side of the service disconnecting means
With that said, I believe it was permitted up to 2002 or 2005 to supply secondary structures using a feeder without an EGC, as long as the grounded conductor was bonded to equipment grounding and grounding electrode systems at the secondary structure.