This video tutorial goes over [one way] you can add the ability to give user's roles and specify which permissions those roles have. You would have to build upon this further to include additional features such as role inheritance or user-specific permissions (overrides).

A flexible ACL. You can create rule sin a static (rules in code) or persistent store (rules in db). Has the ability to assign permissions to users, roles, and (soon) role groups. You can create both explicit allow an deny permissions. Users can have multiple roles, roles can inherit from other roles, and user-specific permissions supersede roles permissions. There's an interesting concept called aliases to making your checks against multiple permissions shorter. You can also create a condition where you pass a callback to the checker. There's a laravel package for lock: https://github.com/BeatSwitch/lock-laravel

"many people require some sort of an Acl component to make their lives easier. Of course, Zend framework has an excellent tried and tested Acl component. Also, the framework’s loose coupoling allows to just use a small part of it. Seeing this, I tried implementing Zend’s Acl component into a default CI installation."