13 10. The Peace and Security Council may decide to hold open meetings. In this regard: a. any Member State which is not a Member of the Peace and Security Council, if it is party to a conflict or a situation under consideration by the Peace and Security Council, shall be invited to present its case as appropriate and shall participate, without the right to vote, in the discussion; b. any Member State which is not a Member of the Peace and Security Council may be invited to participate, without the right to vote, in the discussion of any question brought before the Peace and Security Council whenever that Member State considers that its interests are especially affected; c. any Regional Mechanism, international organization or civil society organization involved and/or interested in a conflict or a situation under consideration by the Peace and Security Council may be invited to participate, without the right to vote, in the discussion relating to that conflict or situation. 11. The Peace and Security Council may hold informal consultations with parties concerned by or interested in a conflict or a situation under its consideration, as well as with Regional Mechanisms, international organizations and civil society organizations as may be needed for the discharge of its responsibilities. Voting 12. Each Member of the Peace and Security Council shall have one vote. 13. Decisions of the Peace and Security Council shall generally be guided by the principle of consensus. In cases where consensus cannot be reached, the Peace and Security Council shall adopt its decisions on procedural matters by a simple majority, while decisions on all other matters shall be made by a two-thirds majority vote of its Members voting.