Entrust is a fantastic role-based permission library for Laravel. However, by design, it only supports attaching permissions to roles, not to users.
This gist adds support for user-specific permissions on top of existing roles.
There's a chance that this hasn't been thought out fully, so use it at your own risk... I'm offering zero support for this. It either works, or it doesn't.
This has only been tested on Entrust's Laravel 5 branch.