Announcement made by Abdel Kader Hatem, spokesman for President Nasser.  The justification for it was Egypt’s alleged rights of self-defense both under the United Nations Charter and under Article Ten of the Constantinople Convention of 1888:

No Israel flagship will be allowed to pass through the Suez Canal.”

“Egypt will therefore take whatever measures she deems necessary for the safety of the canal, which is an integral part of her territory.

She will exercise the right fully and will hold fast to it, for it is her legal right as stated in Article 51 of the United Nations Charter, which says that every state is entitled to exercise the right of self-defense.  No power in the world will prevent Egypt from exercising this legal right of hers.”

Source: Regional Development for Regional Peace: A New Policy and Program to Counter the Soviet Menace in the Middle East, Washington, DC: Public Affairs Institute, 1957