Henrik Olsen & Stuart Toddington 
Law in its Own Right [PDF ebook] 

What, precisely, is the relationship between legality and morality? Does legal validity rest upon moral validity? Are legal obligations moral obligations? For some years now schools of jurisprudential Naturalism and Positivism have become increasingly ambiguous in their responses to these questions. Olsen and Toddington argue that equivocation on the central issue here – that of obligation – has brought legal theory to the point where leading legal positivists and natural lawyers no longer retain significant differences. Instead, they allege, we are left with the remnants of what has always been, philosophically, a phoney war.
The authors of this lucid and refreshing analysis of the concept of law, arguing from the perspectives of social science and political philosophy, show that jurisprudence must acknowledge that the
political, the moral, and the legal are located within a continuum of practical reason, and that law”s ”autonomy” from morality can not entail its ”separation” from it.