User privileges

Hello,

I have created a database (testdb) and given users trusted access to it
from a single machine.
host testdb xxx.xxx.xxx.xxx 255.255.225.225 trust
xxx.xxx.xxx.xxx is substituted with the real IP address

A user does not have, by default, any access to tables and is dependent
upon the database owner to grant them. The database owner has created
tables and granted various access permissions to users for those
tables. This all works as expected.

What I didn't anticipate was that users , by default, would be able to create
tables within this database and grant access permissions on them.
I do not want this functionality and need to switch it off somehow.
I have looked for ways to do this within the sql commands CREATE DATABASE
and GRANT, but cannot find anything.

1. How can I deny users the ability to create tables within a database
yet still allow them access to existing tables created by the
database owner ?

Your help would be most appreciated.

Many Thanks
Maggie