Second, the Parties to a treaty seldom explain in the latter why and to
what extent a certain relevant circumstance was taken into account when
drawing a maritime boundary. For this very reason, it is difficult to find
evidence of opinio juris in State practice. On this point, there is an inherent
difficulty in identifying customary rules in the field of maritime delimitation.
Hence, it is hardly surprising that international courts and tribunals
have to rely mainly on judge-made law in this particular field.