bin group strange permissions

I was doing a little playing around with permissions on a 5.3 box in the office and wanted to make it so that it does not take root permission to delete a users home directory once they are deactivated or deleted in smit.
the default permissions are 755 with bin as both user and group
I noticed that if i change the permissions to 775 and give a typical user group membership in bin he can not delete a file in that folder.
I noticed also that if i change the group ownership of the directory to staff, (which my user also has membership) folders contained inside I can delete.

is there something special about the bin group that would prevent even a user who has group membership from being able to take advantage of them when bin is the group owner of the folder?

Inside a users home directory normally the user himself - using his primary group, which is usually "staff" - creates directories/files. So they have an ownership of "<user>:staff" in most cases. Why should you be able to delete these when you are a member of "bin" or any other group, except "staff"?

Was this your problem or is there more to it?

bakunin

i think you have pegged it. It seems if i change the group permission of the /home directory to something like itusers and give 770 access to it then I am able to log in to my directory but if cd out of it with out at least 771 permission i can't get back in. The original thought was to only allow it users without root permission to clean up employees invalid home directories after they leave the company.