Would it be possible for NATO to intervene in Ukraine? (explained from a legal perspective)
In the event that NATO decided to intervene with military forces on Ukrainian territory, the fifth article of its Founding Treaty makes the approval of these actions subject to the Security Council, where Russia and its Chinese ally are included in.
But what exactly does article 5 of the NATO Founding Treaty say?:
Article 5 The Parties agree that an armed attack against one or more of them in Europe or North America shall be considered an attack against them all and consequently they agree that, if such an armed attack occurs, each of them, in exercise of the right of individual or collective self-defence recognised by Article 51 of the Charter of the United Nations, will assist the Party or Parties so attacked by taking forthwith, individually and in concert with the other Parties, such action as it deems necessary, including the use of armed force, to restore and maintain the security of the North Atlantic area.
Any such armed attack and all measures taken as a result thereof shall immediately be reported to the Security Council. Such measures shall be terminated when the Security Council has taken the measures necessary to restore and maintain international peace and security.
On the other hand, according to the Charter of the UN in its article 27 regarding the Security Council it is provided that:
“Each member of the Security Council shall have one vote. Decisions of the Security Council on procedural matters shall be taken by the affirmative vote of nine members".
Nevertheless, we have to keep in mind that since 1972, the Soviet Union (and since 1991, Russia) has used its veto power in the Security Council more than any other permanent member. Actually they have used their veto 103 times, more than any other of the five permanent members of the Security Council.