What I mean by “stupid things” is not going out and having drink (or more than one) with your friends during off hours. I mean causing major trouble, mayhem (in French called “Trouble à l'ordre public”) like fighting in bars (or even completely destroying them, for the ‘fun’, like I've seen it done, not by legionnaires) anything that could take you to the nearest police station in custody for a few hours. You'll be pinpointed as a trouble maker and if this happens too frequently this will definitely be an issue. And I'm not even talking about more serious things like stealing a car, having a car crash and killing people (even worse if you're intoxicated), etc. etc. (real examples). Just keep in mind that if you run into such major trouble, the Legion will not do anything for you. Those days are gone. You'll be tried and jailed in a civilian prison and kicked out of the Legion.
I am curious what common stupid things some bad legionnaires get into "shit" for.