Just for info: I had a similar issue. I needed to check a table of permissions in the same database as the entity I wanted to authorize. It turned out that I could invert the process and authorize the entity with the permissions instead of the real entity I wanted to authorize.
I could do this as I had a table higher in the object graph that was a fk to both the permissions table and the table I really wanted to be authorized.
This means I don't need to use another adapter in the authorizer just to get the permissions.
I guess I could always have used the authorizing logic in my application code, but using the Authorizer this way means that code is in one place.