Depends on which resolution your are talking about.

yes

Iraq

No.

Just to give one example, some nations are members of the UN "Security Council" and others aren't. Any Security Council nation can veto a UN resolution.

Since most nations of the world are in the United Nations, all of the countries fighting in Iraq and UN member states.

The US has in the past used Iraq's material breach of United Nations Security Council Resolutions 1441 and 687 to justify the invasion of Iraq. Despite United Nations Security Council Resolution 1483 later recognizing US/UK jurisdiction over Iraq as legal, the invasion was never supported by a Security Council resolution.