For David in particular, the UN Security Council and vetos.
The UN Charter doesn't talk about vetos, instead it says (Chapter V, Article 27) that "Decisions of the Security Council . . . shall be made by an affirmative vote of nine [out of the fifteen] members including the concurring votes of the permanent members."
So if one of the five permanent members says no, the resolution falls.
To see who has done this, have a look here. Note in particular which country has been most consistently unreasonable in stopping solutions to the problems of the Middle East.