Which is best for ACL?

[eluser]Kemik[/eluser]
Hello,

I'm creating a fairly complicated user system. A user can be one of the following, with each group given different permissions.

Admin Groups
Site Admin (root)
General Admin
News Admin
Competition Admin
Referee
Site User

Users and admins can also be a member of a clan (aka team)

Clan Permissions
Clan Leader (all clan permissions)
Clan Member
Manage Applications
Manage Fixtures
User awaiting member approval

E.g. Bill is clan leader and has access to all clan actions. Bob is a clan member with the ability to manage applications. Fred is a clan member with both manage applications and manage fixtures.

As you can see, it's sort of a two tier permission system. A user can only be one of the "Admin Groups" but can also (optionally) be one of the "Clan Permissions".

Which library do you feel would be best to manage this kind of system? I don't need the frontend area for users/admins to edit details as I've already created that. Just need something that manages the database side of things and I can do to check if the user has the permission to do the action.

Thanks for your help.