Nested tables

I've looked through the documentation, but I've not found anything that
addresses this situation. Is this possible with PostgreSQL? Or maybe there is
a better way to accomplish what I want to do?

Basically, I'd like to set up an ACL-like property for each record. A table
could be strucured like this:

Table ACL:
Attribute | Type | Modifier
---------------+-------------+----------------------------
uniqid | varchar(12) | not null
date_created | timestamp | not null
date_modified | timestamp | not null
read | boolean | not null default 'f'::bool
write | boolean | not null default 'f'::bool
execute | boolean | not null default 'f'::bool
delete | boolean | not null default 'f'::bool

Table myItem:
Attribute | Type | Modifier
----------------+-------------+----------
uniqid | varchar(12) | not null
date_created | timestamp | not null
date_modified | timestamp | not null
author | text | not null
title | text | not null
access_control | acl | not null

PostgreSQL lets me create the class myItem with a "acl" field type, but I
can't figure out how to insert multiple values (or any values!) into the
access_control field...

Thanks,
Jason