Look at 408.21. It clearly prohibits this even if the lug is listed for more than one termination. This has been a UL listing requirement for a long time and has just been made into a code section since know one new it was there.
You have to read the fine print that comes with the service panel. Most times it says, "You can install two or more "GROUNDING" conductors if they are the same size. That would be the bare ground wire. Not the neutral or the "GROUNDED" wire. I believe the 2002 NEC just help to clarify this issue. My state still goes under the 1999 NEC for now.