Quite honestly, I had never heard of Kelsen before. Perhaps this is unsurprising, considering the almost complete lack of theory in the law school curriculum. I also never encountered him in my studies of history, philosophy or literary theory, but then again, I’m hardly a specialist in such matters. So I found the following discourse interesting as a pointer to a new (for me) area of legal studies.
On the first question, it seems to me clear that competent philosophers of law need (at a minimum) a basic acquaintance with Kelsen’s theory. One place to start would be Green’s paper (cited above), but an even better starting point would be Stanley Paulson’s Introduction to Normativity and Norms: Critical Perspectives on Kelsenian Themes, a magnificient anthology now sadly out of print (but still available via the link at Amazon.com). I assume that no one would seriously dispute this point, because of Kelsen’s importance in the history of legal philosophy–significant even in the Anglophone Hart-Dworkin-Raz-Finnis tradition and enormous in continental philosophy of law. (A similar point could be made about the more recent work of Niklas Luhmann, e.g., his Law as a Social System.)
On the second question, I think that anyone who works on the what-is-law, what-are-the-necessary-qualities-of-law, nature-of-law debate should have a basic familiarity with Kelsen’s work in translation, e.g., with Pure Theory of Law and General Theory of Law And State. Basic familiarity is not mastery. Because Kelsen’s writing is abstract, complex, and frequently obscure, mastery would come at a high cost–in my opinion, only through careful study of Kelsen in the original German. (Yes, I really mean this. Quite obviously, anyone who writes a dissertation on Kelsen should read him in German.)
So what gives? What is there about Kelsen that Americans don’t like?
The problem, I think, is that Kelsen/s approach runs against the two dominant trends in American philosophy of law. Most Americans look at law and legal systems empirically–as fundamentally involving questions of social facts. The competing view, represented by Dworkin and Finnis, considers legal facts to be, at least in part, moral facts.
Kelsen rejected both views. For him, the law was neither empirical nor moral. The best analogy I can think of is the way many philosophers talk about language. A language correlates certain physical things (e.g. strings of letters or phonemes) with linguistic meanings. For example, “Es regnet” means it rains in German (but nothing in English). For Kelsen, legal systems correlate certain social events (people raising their hands in a room) with legal meanings (a statute being enacted). And just as many philosophers consider linguistic meanings to be abstract objects–neither empirical nor moral–Kelsen thought the same thing was true of legal meanings.