The point of the treaty is to come to an agreement between two governments. If the provisions of the treaty are not legally possible than the treaty is meaning

The point of the treaty is to come to an agreement between two governments. If the provisions of the treaty are not legally possible than the treaty is meaningless. For a more extreme example: If the US congress signs a treaty with England which agrees that the US Presidents will no longer have any power in exchange for the English Prime Ministers too also no longer have any power, it doesn't matter because congress didn't have the power to write such laws in the first place.