If I understand correctly the following (point & from GA TOS):

1. PRIVACY . You will not (and will not allow any third party to) use the Service to track or collect personally identifiable information of Internet users, nor will You (or will You allow any third party to) associate any data gathered from Your website(s) (or such third parties' website(s)) with any personally identifying information from any source as part of Your use (or such third parties' use) of the Service. You will have and abide by an appropriate privacy policy and will comply with all applicable laws relating to the collection of information from visitors to Your websites. You must post a privacy policy and that policy must provide notice of your use of a cookie that collects anonymous traffic data.

You are not allowed to use custom variables that will identify the visitor(for example website username, e-mail, id etc.) So the question is how can I track a specific user behaviour(for example the actions that every single logged in user do).