With respect to the principle of the tacit or tacit concept arising from the aforementioned common law, there is no doubt that the Tribunal will be compelled to bear in mind the provisions, principles and values of the Constitution when it hears a tacit or tacit term in an agreement, since the Constitution obliges the courts to develop the common law in a way that conforms to constitutional values. In another context of the Treaty Interpretation Act, a similar restrictive approach was adopted in the City of Tshwane Metropolitan Municipality against Blair Atholl Homeowners Association  1 All SA 291 (SCA), where the SCA followed the recent tendency of the High Courts to allow evidence likely to interpret the terms of a written agreement. He confirmed that evidence of previous negotiations in the interpretation of the terms of a written contract is inadmissible, except perhaps in very exceptional circumstances. Although it remains very important that the terms of a legal document be interpreted within its framework and in its general context, Blair Atholl has been pruned according to the principles of extrinsic evidence, always reaffirmed by the Joint Pension Fund Natal/Endumeni Municipality 2012 (4) SA 593 (SCA). It can rightly be said that, in the above case, the legal motivation of the Court of Justice has, on the whole, qualified a single – or regularly absent – argumentative rigour. This case differs from international court decisions in its careful distinction between the criteria necessary to establish the existence of a legal construct and those used to determine the content of those agreements. In Peru/Chile, the Court of Justice, after finding that the 1952 Santiago Declaration is an international treaty, stressed that the issue was no longer a matter of legal identification, but a matter of substance, and that the Court`s subsequent task was to “verify whether it establishes a maritime boundary between the contracting parties”.  The Court was therefore very cautious in separating the conclusion of the treaty and its content, pointing out that the criteria for the execution of the former are not necessarily the same as those used to achieve the latter. The Court thus resorted, after answering the question of the legal nature of the 1952 declaration, to traditional techniques for determining the content of the interpretive doctrine, as contained in Articles 31 and 32 of the Vienna Convention on Treaty Law.  Applying these traditional content definition techniques, the Court found that the 1952 declaration did not establish an agreement on a maritime border between the two countries.  This finding led the Court to then consider the nature and content of the additional convention to the Santiago Declaration of 1952, the Convention on the Monitoring and Control of The Maritime Areas of the Signatory States, the 1954 Special Maritime Border Agreement and the 1968-1969 Lighthouse Construction Agreements to verify that they have reached an agreement between the parties on their maritime border.  The Court of Justice`s well-argued thoroughness and its careful distinction between legislative identity and substantive provision were immortalized in the revision of these various instruments.