At the beginning of Measure for Measure, it is understood that the Duke has let the law slip a bit, and fears that it would now be impossible to re-implement it. The people no longer take it seriously and have become increasingly rowdy and badly behaved. So, knowing he cannot effectively enforce the law after not doing so for so long, he appoints Angelo to do it. Angelo will lead without mercy. He will prove to the people that the law must be taken seriously, making examples of those who disobey. This seems to be the Duke’s goal, but the way the rest of the play works out, it may be a goal to which he is not very committed.
Angelo starts things off by sentencing Claudio to death, making a very bold statement to the people of Vienna. Claudio’s crime is not particularly heinous, (in fact, by our modern standards, there’s nothing about it that could even be considered a crime) yet he’s received the harshest of punishments: execution. At this point, we can reasonably understand why the Duke would slip in to undo this sentence. Perhaps Angelo has taken the Duke’s instructions a little more strongly than he had expected, and doesn’t want to see Claudio die for what he’s done. So in this case, the Duke goes against his wish to see the law strongly enforced. His merciful nature has gotten the best of him, and it’s understandable regarding this case of such a victimless crime with a very harsh punishment. But there are two other characters who less deservedly get the Duke’s mercy, all while he was originally trying to strengthen the law: Pompey and Barnadine.
Pompey has broken the law in some sense, though it is not entirely clear how. He frequents brothels and is said to be a thief. Certainly this is the kind of criminal who can rightly be made an example of, if that’s what the Duke is really looking to do. Yet, there is no word of punishment for him. When the Duke is looking for someone to be executed instead of Claudio, Pompey isn’t even considered. Barnadine is considered, though. We don’t really get any information on why he is in prison, but we know he’s been in there for nine years, and his behavior hasn’t really improved the entire time. The Duke then calls for his head, but is relieved to find out that a “most notorious pirate” who looks a bit like Claudio has died that morning. The Duke calls it “an accident that heaven provides.” Then, at the end, the Duke pardons Barnadine entirely.
My question is, what happened to the Duke’s original intentions? He’s associating freely with criminals, pardoning long-term prisoners who haven’t shown signs of improvement, and doing his best to undo the first authoritative act of the man he appointed.