RESOLVING THE PARADOX OF OPINIO JURIS

I suggested in the preceding chapter that opinio juris be interpreted as a requirement that states generally believe that it is desirable now or in the near future to have an authoritative legal principle or rule prescribing, permitting, or prohibiting certain state conduct. This revised definition of opinio juris helps to resolve the “paradox” of opinio juris described in Part One.

This definition is based in part on insights of J.M. Finnis. Finnis' solution to the paradox is this: He argues that at the root of opinio juris are two related practical judgments. The first is that in some domain of human affairs “it would be appropriate to have some determinate, common, and stable pattern of conduct and, correspondingly, an authoritative rule requiring that pattern of conduct” and that “to have this is more desirable than leaving conduct in this domain to the discretion of individual states.” The second is that “this particular pattern of conduct…is appropriate, or would be if generally adopted and acquiesced in, for adoption as an authoritative common rule of conduct.”

Finnis maintains that when “the contents of a multilateral treaty, or the resolutions of an international body representative of states, are spoken of as sources or evidence of custom, what is really (or, at any rate, justifiably) being said is that the treaty or resolutions are evidence not of an opinion about what the law already is, but of opinio juris in the limited sense expressed in these two judgments…. They affirm that something is desirable (a) in general, (b) in particular.”