NIS overrides with user groups

[Ben 'Bend Over' Dover]

The last couple of days I have bin trying to setup a box to authenticate
users from a NIS server. With the help of the Handbook pages I've done
that and it works.
But I can't seem to get to only add users from a specific normal group to
the client.

According to the 4.9-Release passwd man pages:
>Using groups instead of netgroups for NIS overrides
>FreeBSD offers the capability to do override matching based on user
groups >rather than netgroups.  If, for example, an NIS entry is
specified as:
>	   + at operator:::::::::
>the system will first try to match users against a netgroup called
>`operator'.  If an `operator' netgroup doesn't exist, the system will
try >to match users against the normal `operator' group instead.

I understood this to be that if operator isn't a netgroup but normal group
this should only add users from the NIS-server that belong to that group.
But I can't get it to work!

Did I understand this wrong or have someone else experienced this problem?

I'd just like to know if this is possible to accomplish or not!