Before I start, let me say two things. First of all, to the extent that John Finnis is entering a plea for more attention to what is a relatively neglected tradition (in the narrow his message a hundred percent. And you courd learning about the natural law tradition than by reading his book, Natural Law and Natural Rights. My second introductory observation is that Finnis and I agree about many more things than you might expect if you just think of him as a natural law theorist and me as a utilitarian. I am very eccentric as a utilitarian. He is, not eccentric, at least unusually advanced as a natural law theorist. actually agree about quite a lot (although of course we also disagree about some important things).
Regan, Donald H. "What a Sensible Natural Lawyer and a Sensible Utilitarian Agree about and Disagree about: Comments on Finnis." J. Legal Educ. 36 (1986): 496-500.