No state consent is required — option 4.

The provision. Article 253 says that notwithstanding anything in the preceding provisions of the chapter, Parliament has power to make any law for the whole or any part of India for implementing any treaty, agreement or convention with any other country, or any decision made at an international conference, association or other body.

The words “notwithstanding anything in the foregoing provisions” are the operative ones: they override the ordinary distribution of legislative power. Parliament may therefore legislate even on a subject in the State List if the purpose is to give effect to an international obligation, and it need not consult any state.

Why the framers gave this power. A treaty binds India as a single international person. If implementing it required the agreement of the states, a single dissenting state could put the country in breach of its obligations. Entering into treaties is an executive function of the Union under Article 73 and Entry 14 of the Union List, and Article 253 makes sure the legislature can complete what the executive has undertaken.

Laws made under it include the Environment (Protection) Act, 1986, passed after the Stockholm Conference; the Air (Prevention and Control of Pollution) Act, 1981; the Protection of Human Rights Act, 1993; and legislation giving effect to the Chemical Weapons Convention — several of which touch subjects otherwise belonging to the states.

Hence, the answer is without the consent of any State.