DTAA incorporation: notification requirement under domestic law limits automatic treaty application across countries and clarifies temporal scope.
The decision holds that a DTAA requires a mandatory notification under Section 90(1) to be effective domestically, that provisions in a DTAA with one country do not automatically extend to other bilateral agreements without explicit amendment, and that the present-tense term "is" fixes the temporal application of treaty benefits to the date of treaty entry with India.

Most favoured nation clause interpretation guides treaty effect, subject to domestic notification requirements for implementation.
The Most Favoured Nation (MFN) clause in tax treaties must be interpreted under Article 31 VCLT principles as reflecting customary international law, with subsequent agreements and state practice serving as authentic means of interpretation. Domestic implementation procedures materially affect treaty operation: comparative practices of other states cannot substitute for India's requirement of formal domestic steps, including issuance of a notification after a treaty trigger event, to assimilate treaty amendments into national law.

Treaty implementation procedures determine when DTAA modifications bind taxpayers, requiring domestic notification for enforceability.
In India, DTAA modifications take effect only upon formal domestic notification, preventing automatic retroactive application of third country treaty changes and reflecting a dualist approach requiring assimilation of treaty amendments into domestic law before they bind taxpayers; by contrast, the Netherlands, France, and Switzerland rely on differing domestic mechanisms-executive decrees, parliamentary ratification, or referenda and implementing orders-that may permit retroactive application and integrate treaties into domestic enforceable law.

Interpretation of "is" in tax treaties determines when OECD membership triggers treaty benefits under domestic implementation rules.
Interpretation of the term "is" in DTAAs is context-dependent: although generally present in signification, its temporal application must be determined from the treaty text and purpose. Applied to OECD membership, the operative moment for eligibility to treaty benefits depends on when the DTAA relationship produces the relevant legal consequence, and this assessment must be reconciled with the domestic requirement for legislative action or notification for treaty enforceability.

Treaty Enforcement: legislative enactment required for treaties to create domestic rights; executive negotiation alone is insufficient.
Treaties do not function as self-executing domestic law; the Union may negotiate and ratify international agreements but legislative enactment is required to create or alter domestic rights and obligations. Under the dualist approach, executive negotiation and foreign measures cannot substitute for domestic incorporation; implementing statutes and notification mechanisms are necessary for tax treaties to be recognized and applied by revenue authorities. Courts may consult treaty texts to resolve ambiguities in domestic implementing laws but cannot themselves import treaty provisions into domestic law absent parliamentary enactment.