A question which was much discussed in legal literature in the early years of the United Nations, and which has been cited as a classic example of the effect of subsequent practice upon a provision in a multilateral treaty, has recently been raised again. This concerns the interpretation of Article 27, paragraph 3, of the Charter of the United Nations, which deals with voting in the Security Council on non-procedural matters. Both Portugal and South Africa last year reserved the position of their governments regarding the validity of Security Council Eesolution 221 of April 9, 1966, in the vote on which both France and the Soviet Union abstained. This is the resolution by which the Council, acting under Chapter VII of the Charter, called for certain measures to enforce an embargo on oil and petroleum products from reaching Southern Ehodesia through the port of Beira in Mozambique, and authorized the United Kingdom to prevent by the use of force, if necessary, the arrival at Beira of vessels reasonably believed to be carrying oil destined for Rhodesia.