Question : Restrict DCHP  / Issue different Default Gateway to Domain Members

Is it possible to restrict issuing of DHCP leases to Domain Members only? Or to issue a different default gateway based on Domain Membership?

From what I know already and research so far it does not look to be possible.

Group Policy currently points Domain Members to an ISA Proxy Server via IE Settings.
I would like to ensure that non-domain members which connect to the network are either directed to the Proxy or, directed to a different Default Gateway (which is on a connection which is restricted via another method.).

Is the only way to do this for the Router/Firewall that is normally issued as the default gateway (and is the Gateway for the ISA Server) to only accept web traffic from the ISA Server?

Or is there a way to only issue DHCP Leases to Domain Members?
Given PXE booting exists I'm assuming DHCP is picked up long before Domain Credentials are checked for?

Answer : Restrict DCHP  / Issue different Default Gateway to Domain Members

No, you can have multiple scopes on one DHCP server.  I use one Server 2003 DHCP server to farm out 97 different scopes for 92 different locations.