The Powers which have signed the abortive Treaty of Washington of 1922 relating to the use of Submarines and Noxious Gases in Warfare, concluded the Treaty of London for the Limitation and Reduction of Naval Armaments of 22 April 1930. Article 22 deals with the use of submarines in warfare. It was laid down in the Treaty that this Article - being declaratory of international law - should remain in force without limit of time (Article 23). Accordingly, when the Treaty of 1930 expired on 31 December 1936, Article 22 remained in force. However, in view of the last paragraph of Article 22, which states that the Contracting Parties invite all others Powers to express their assent to the rules embodied in this Article, a procès-verbal was signed on 6 November 1936 which incorporates verbatim the provisions of Article 22 of the Treaty of 1930. A considerable number of States acceded to this procès-verbal.