Well, remember, this would be in the context of a criminal offence having been committed--they would be before the court for that--and also in the context, with your clarification, of there having been previous criminal offences committed, although perhaps not a conviction yet. There would have been breaches. I would hope that would show the intent of “good conduct”--to, in other words, not commit further criminal offences.
It would not be that dissimilar from the phrase “keep the peace and be of good behaviour”, which is used, as you know, all the time.