Explanation:

The word sovereign in Preamble has the following bearing:-

Sovereignty, in short, means the independent authority of a state. It has two aspects- external and internal. External sovereignty or sovereignty in international law means the independence of a state of the will of other states, in her conduct with other states in the comity of nations. Sovereign in its relation between states and among states signifies independence.  The external sovereignty of India means that it can acquire foreign territory and also cede any part of the Indian territory, subject to limitations(if any) imposed by the constitution.

On the other hand, internal sovereignty refers to the relationship between the states and the individuals within its territory. Internal sovereignty relates to internal and domestic affairs and is divided into four organs, namely, the executive, the legislature, the judiciary and the administrative Article 51 in Directive Principle of State Policy clearly delineate the principles of India’s relation with foreign countries. It states that ‘To promote international peace and security and maintain just and honourable relations between nations; to foster respect for international law and treaty obligations, and to encourage settlement of international disputes by arbitration.

In Part XI of the Constitution which describes Union and State relations have given authority to the Parliament to make laws to implement International Agreements. The Parliament can make laws on any matter in the State List for implementing the international treaties, agreements or conventions. This provision enables the Central government to fulfil its international obligations and commitments. Besides, Seventh schedule of the Constitution mentions foreign relation under Union list.