The scene in Case-1 illustrates an attractive and popular scenario for understanding the law and its efficacy. It is constructed from two stories, one on law’s efficacy and one on behavioural choice. These two combined represent the utility perspective on the law: one ought to choose one’s behaviour to tally with one’s welfare.
The utility perspective is often opposed to what I will further call the autonomy perspective which orders that one ought to choose one’s behaviour to tally with one’s duty (whatever that happens to be — the autonomy perspective is often considered to be deontologic in nature).
Nobody submits that the utility perspective and the autonomy perspective exclude each other. Of any behaviour can be said that it not only influences welfare, but also that it is someone’s duty (or not). Distinguishing the perspective is useful because in legal philosophy Kant, Nietzsche and Mill tend to be influential, and their positions (despite their rather extreme differences in opinion) can be usefully related to these perspectives.