UPDATE 7:02 ET: Joe Strauss just tweeted this:
Regarding S. Miller suspension: If you are 20 years old there are certain things you're not allowed to do. And certainly not multiple times.
Unless Joe is talking about getting a rental car here, one has to assume this suspension is due to the use of alcohol.
Miller is currently pitching for the Cardinals Double-A affiliate in Springfield and missed his start on Thursday. Updates as they come.