The Legal Theory Bookworm recommends Oxford Studies in Philosophy of Law: Volume 2, edited by Leslie Green and Brian Leiter. Here is a description:
Oxford Studies in the Philosophy of Law is an annual forum for some of the best new philosophical work on law, by both senior and junior scholars from around the world. The essays range widely over issues in general jurisprudence (the nature of law, adjudication, and legal reasoning), the philosophical foundations of specific areas of law (from criminal law to evidence to international law), the history of legal philosophy, and related philosophical topics that illuminate the problems of legal theory. OSPL will be essential reading for philosophers, academic lawyers, political scientists, and historians of law who wish to keep up with the latest developments in this flourishing field.