Neutral/ground bond in subpanel

Does anyone know the correct code reference to the fact that the neutral and ground wires are not bonded together in a subpanel? The only reference I can find in the IRC2003 is paragraph E3507.3.1 if I read it correctly -
I know, we are not code inspectors, but I have a client that is trying to get his electrician to fix a subpanel and the electrician is arguing with him about how the subpanel was wired. I called it out and the owner agrees with me, but the electrician wants to argue to keep from fixing his screw up -
Subpanel is to a steam room - taken off the main panel with a 220v 50A breaker and feeds a 50A GFCI - all wires are correct but he bonded the ground and neutral in the sub on the same bus bar and tied it all together on the enclosure -
Thanks to all you Sparkies - you have taught me a lot in all these posts -

You can start with this. . .

408.20 Grounding of Panelboards. Panelboard cabinets and panelboard frames, if of metal, shall be in physical contact with each other and shall be grounded. Where the panelboard is used with nonmetallic raceway or cable or where separate grounding conductors are provided, a terminal bar for the grounding conductors shall be secured inside the cabinet. The terminal bar shall be bonded to the cabinet and panelboard frame, if of metal; otherwise it shall be connected to the grounding conductor that is run with the conductors feeding the panelboard.

Grounding conductors shall not be connected to a terminal bar provided for grounded conductors (may be a neutral) unless the bar is identified for the purpose and is located where interconnection between equipment grounding conductors and grounded circuit conductors is permitted or required by Article 250.

If you go to Paul Abernaty’s site,the he may still have a great presentation on grounding and bonding.

I think it is posted here on the NACHI site too.

I would post it here ,but the file is to big.

Email me if you want a copy.