In Montreal, on 1 March 1991, at the close of the International Conference on Air Law (12 February–1 March 1991), participating States sign the Convention on the Marking of Plastic Explosives for the Purpose of Detection. The authentic texts are English, French, Russian, Spanish and Arabic; the depositary is the Secretary General of the International Civil Aviation Organization (ICAO). The Convention is open for signature in Montreal on 1 March 1991 and thereafter at ICAO Headquarters until entry into force.

The preamble expresses concern at acts of terrorism, including those aimed at aircraft, and notes the use of plastic explosives; recognises that marking such explosives for detection would contribute significantly to prevention; recalls Security Council Resolution 635 (1989), General Assembly Resolution 44/29 and ICAO Assembly Resolution A27-8 on an international instrument for marking plastic or sheet explosives.

Article I defines explosives (products commonly known as plastic explosives, including flexible or elastic sheet form), detection agent, marking, manufacture, duly authorized military devices and Producer State. Article II requires each State Party to prohibit and prevent the manufacture in its territory of unmarked explosives. Article III prohibits and prevents the movement into or out of its territory of unmarked explosives, with limited exceptions for military or police authorities.

Article IV requires strict control over stocks of unmarked explosives existing at entry into force: stocks not held by military/police authorities must be destroyed, consumed for consistent purposes, marked or rendered permanently ineffective within three years; military/police stocks not incorporated in authorized devices, within fifteen years. Articles V–VII establish the International Explosives Technical Commission (15–19 experts appointed by the ICAO Council) to evaluate technical developments and propose amendments to the Technical Annex.

Article XIII provides that the Convention shall enter into force on the sixtieth day following deposit of the thirty-fifth instrument of ratification, acceptance, approval or accession, provided that no fewer than five such States have declared that they are producer States. The Convention enters into force on 21 June 1998; it is registered in the UNTS as No. 36984 (volume 2122).

The present text concerns the Convention signed at Montreal on 1 March 1991; the Technical Annex, an integral part, lists the agreed detection agents for marking.

Image: ICAO Headquarters, Montreal; Wikimedia Commons. Cropped to 16:9.

Source consulted: Convention on the Marking of Plastic Explosives. Treaty text: Convention on the Marking of Plastic Explosives for the Purpose of Detection, Montreal, 1 March 1991.