You can put a EULA screen on enrollment and append a notification to the log in screen. However, I don't think you can add an "extra" step to log in that forces a log out if not completed.
In theory you could use a policy with JAMF helper to run a log in, that could force a log out depending on which option is selected in the dialog. Though I am not sure how reliable this would be, and JAMF Helper could just be quit as it's a program.
We have a training course that people must take every year which covers our terms of use. If they fail to take that course, they get fired. Kinda solves the problem if that is the angle you are working from.
