The UN Charter , in its Preamble , set an objective: "to establish conditions under which justice and respect for the obligations arising from treaties and other sources of international law can be maintained". Ever since, the development of, and respect for international law has been a key part of the work of the Organization. This work is carried out in many ways - by courts, tribunals, multilateral treaties - and by the Security Council, which can approve peacekeeping missions, impose sanctions, or authorize the use of force when there is a threat to international peace and security, if it deems this necessary. These powers are given to it by the UN Charter, which is considered an international treaty. As such, it is an instrument of international law, and UN Member States are bound by it. The UN Charter codifies the major principles of international relations, from sovereign equality of States to the prohibition of the use of force in international relations.
I would consider aiddng new elements (particularly standalone elements) a last resort in just about any case. If an element is to be created like hgroup it makes a ton of sense for it to be one that leverages and adds value to existing elements, rather than simply standing on its makes a great point about the semantic flaws in grouping heading elements. But I see an easier path for browser makers and designers in interpreting headings within an hgroup than the path to uniquely interpreting an entirely new standalone element.