Google Adsense is an example of a cookie that can be prevented, but once it's set there is no way for EU e-Privacy Directive to remove it because of the Same Origin Policy. This is what you will see if you're using Adsense. These cookies will remain after a user has chosen to remove cookies. This is OK though. As long as you prevent them from loading initially, when the user accepts cookies - it's Google who is placing these additional cookies on their computer.
This is what it looks like. Don't lose your mind trying to find a way to remove them.