Retro amendments don't automatically alter analogous DTAA provisions and can't be read into DTAA provisions

WNS NORTH AMERICA INC. v. ADIT (Mumbai - Trib.)   If a particular term has been specifically defined in the treaty, the retrospective amendment to the definition of such term under the Act would have no bearing on the interpretation of such term in the context of the Convention. In the instant case, the Mumbai Tribunal decides on the issue of applicability of retrospective amendments to the provisions of treaty as under: Para 1 of Article 23 of India-Mauritius treaty provides that "the laws in force in either of the Contracting States shall continue to govern the taxation of income in the respective Contracting States except where provisions to the contrary are made in this Convention"; When we read full text of Para 1 of Article 23, it becomes manifest that if there is some provision in the Treaty contrary to the domestic law, then it is the provision of the treaty which shall prevail; If the retrospective amendment is in the realm of a provision of which no contrary provision is there in the Treaty, then such amendment will have effect even under the DTAA and vice versa; If a particular term has been specifically defined in the Treaty, the amendment to the definition of such term under the Act would have no bearing on the interpretation of such term in the context of the Convention;  A country who is party to a Treaty cannot unilaterally alter its provisions. Any amendment to Treaty can be made bilaterally by means of deliberations between the two countries who signed it;  The term "royalty" has been defined in the DTAA as per Article 12(3) of Indo-US DTAA. Such definition of the term "royalty" as per this Article is exhaustive. Pursuant to the insertion of Explanation (5) by the Finance Act, 2012, no amendment has been made in the DTAA to bring the definition of royalty at par with that provided under the Act. Subject matter of the Explanation is otherwise not a part of the definition of Royalty as per Article 12; and  Thus, the retrospective insertion of Explanation 5 to section 9(1)(vi) couldn't be read in the DTAA.