Paul on the Law
It frustrates me when scholars select a poorly chosen category or question and try to force an answer out of an ancient text. They typically then proceed to argue endlessly over various answers that they try to give.
I think Paul's views on the law is an example of one such offender. ("Was Judaism a religion of grace?" is another) In this case, I think the situation is very simple but that scholars have got confused by asking the wrong questions and trying to give answers. Often these issues can be resolved simply by starting with the obvious and seeing what light obvious things can shed on the situation under discussion.
These two statements, I think, may be said to be obvious and universally agreed upon: (1) Paul has certain expectations regarding the moral conduct of Christians. He exhorts his readers to aspire to and achieve moral behavior, and he rebukes his converts when he feels they are falling short of such behavior. (2) Paul is against Gentiles having to follow the rituals of the Mosaic Law.
Those form two poles of Paul's thought. In his rhetoric and arguments he sometimes talks about one, sometimes the other, sometimes both at once. In the course of these arguments he uses the word 'law' in different ways. On the one hand, because Gentiles do not need to follow the rituals of the Mosaic Law, the Law is for them abolished, finished, ended, gone, and irrelevant etc. On the other hand, because these gentile Christians live morally they can be said to meet the moral requirements of the law, obey the commandments, fulfill the law, obey the law of Christ etc.
In other words, the two basic elements of Paul's thought outlined above naturally give rise to him making statements about the law in the course of his arguments that taken literally are inconsistent because he is using the word law in different senses in different arguments. Paul's thinking on this issue is perfectly consistent, but his terminology varies depending of which of his thoughts he is expressing.