Fotis,

It seems that you have 2 'OLD' annoying bugs in Users' Permissions.

Create a new User Group with 'Publish items' to 'No' and with a few categories selected.
Add the J! user to the group (J! group : Manager with ACL option : Edit State set to Denied).
Connect with the user after adding that user to the appropriate group :)

- You can still publish items if you go on the ITEM DETAIL VIEW & switch Published checkbox to Yes (ACL seems t work on the ITEM VIEW LIST).

- IN ITEM DETAIL VIEW : you can still select any categories you want even when you have excluded categories using : Assign group permissions to these categories.

A solution to this is welcome :)