Manchin/Heitcamp Syria Proposal and the Vienna Convention on Treaties

Senators Manchin and Heitcamp are working on an alternative Syria Resolution that tentatively provides:

The failure by the government of Bashar al-Assad to sign and comply with the [Chemical Weapons] Convention clearly demonstrates a disregard of international norms on the use of chemical weapons. If the Government of Syria does not sign the Convention within 45 after the date of the enactment of this resolution, all elements of national power will be considered by the United States government.

A potential problem with this approach is that Article 52 of the Vienna Convention on the Law of Treaties provides: “A treaty is void if its conclusion has been procured by the threat or use of force in violation of the principles of international law embodied in the Charter of the United Nations.”  The United States has not ratified this treaty but the State Department says that the “United States considers many of the provisions of the Vienna Convention on the Law of Treaties to constitute customary international law on the law of treaties.”  Syria has ratified the Convention, as have most countries.  I cannot imagine that Syria will give in to the proposed threat if it became law.  But if Syria were to ratify the Chemical Weapons Convention in the face of this threat, it would have a good argument that the ratification was void.