Each member of the Security Council has one vote. On questions of procedure, a motion is carried if it obtains an affirmative vote of any nine members. On substantive matters, a resolution requires the affirmative votes of nine members, including the concurring votes of the permanent members. However, any member, whether permanent or nonpermanent, must abstain from voting in any decision concerning the peaceful settlement of a dispute to which it is a party.
The veto power and its exercise by permanent members remains a central characteristic of the mechanism of the Security Council, although, since the end of the cold war, a new climate of collegiality has made its use rare. Though the word "veto" does not occur in the charter, it is the common-usage term for the power of any of the five permanent members to defeat a resolution by voting "nay."
Negative votes cast in the council by its permanent members constitute an exercise of their veto power only on substantive questions, not on procedural matters. Moreover, by long-standing practice, the charter provision stipulating that all substantive resolutions must obtain the concurring votes of the permanent members has been interpreted to mean that, provided a permanent member does not actually vote "nay," a resolution may still be carried.
The veto power, then, is the constitutional instrument for giving expression to the requirement—discussed at the opening of this chapter—that before the Security Council invokes its authority in peacekeeping action, the big powers should first resolve their differences on how a particular crisis should be handled. However, although the principle of ensuring unanimity among the big powers was the major consideration underlying the institution of the veto, it was not the only one. A complementary consideration was the need of the major powers to ensure that their decisions would not be overridden by a majority vote of the smaller nations. In effect, conferring the right of veto upon a few powerful countries was tacit acknowledgment of the natural conflict that exists between their interests and those of the less powerful nations. It was a recognition of the fact that, despite differing social systems and power rivalry, the large countries often share more interests with each other than they do with smaller nations having social systems and tenets similar to their own. And it was for exactly this reason that the smaller countries represented at the San Francisco Conference made strenuous but unsuccessful efforts to prevent the institution of the veto power in the charter.