A diplomatic bag, also known as a diplomatic pouch, is a container with certain legal protections used for carrying official correspondence or other items between a diplomatic mission and its home government or other diplomatic, consular, or otherwise official entities. The physical concept of a "diplomatic bag" is flexible and therefore can take many forms (e.g., a cardboard box, briefcase, duffel bag, large suitcase, crate or even a shipping container). Additionally, a diplomatic bag usually has some form of lock and/or tamper-evident seal attached to it in order to deter interference by unauthorized third parties. The most important point is that as long as it is externally marked to show its status, the "bag" has diplomatic immunity from search or seizure, as codified in article 27 of the 1961 Vienna Convention on Diplomatic Relations. It may only contain articles intended for official use. It is often escorted by a diplomatic courier, who is similarly immune from arrest and detention.
In discussions of cryptography, the diplomatic bag is conventionally used as an example of the ultimate secure channel used to exchange keys, codebooks, and other necessarily secret materials. Like Alice and Bob, it is an example of a metasyntactic variable when used this way.
In contemporary practice, diplomatic bags are indeed used for exactly this purpose. An illustration is the strenuous protest made by German diplomats in Poland in the late 1920s when a cypher machine being shipped to the German Embassy in Warsaw – a commercial version of the famous Enigma machine – was mistakenly not marked as protected baggage and was opened, under protest, by Polish Customs. It was released to them, supposedly without much apology (and with still more protest), on the following Monday, but had perhaps been subjected to inspection by Polish cryptography personnel over the weekend.
- During World War II, Winston Churchill reportedly received shipments of Cuban cigars by this means.
- Triplex was a British espionage operation in World War II which involved secretly copying the contents of diplomatic pouches of neutral countries.
- In 1964, a Moroccan-born Israeli double agent named Mordechai Ben Masoud Louk (also known as Josef Dahan) was drugged, bound, and placed in a diplomatic bag at the Egyptian Embassy in Rome, but was rescued by Italian authorities. The crate that he had been placed in appeared to have been used for a similar purpose before, possibly for an Egyptian military official who had defected to Italy several years before but then disappeared without a trace before reappearing under Egyptian custody and facing trial.
- During the 1982 Falklands War, the Argentine government used a diplomatic bag to smuggle several limpet mines to their embassy in Spain, to be used in the covert Operation Algeciras, in which Argentine agents were to blow up a British warship in the Royal Navy Dockyard at Gibraltar. The plot was uncovered and stopped by the Spanish police before the explosives could be set.
- In the 1984 Dikko Affair, a former Nigerian government minister, Umaru Dikko, was kidnapped and placed in a shipping crate in an attempt to transport him from the United Kingdom back to Nigeria for trial. However, it was not marked as a diplomatic bag, which allowed British customs to open it.
- In 1984, the Sterling submachine gun used to shoot dead WPC Yvonne Fletcher from inside the Libyan Embassy in London was smuggled out of the UK in one of 21 diplomatic bags.
- In March 2000 Zimbabwe was the object of political interest internationally when it opened a British diplomatic shipment.
- In May 2008, a replacement pump for the toilet on the International Space Station was sent in a diplomatic pouch from Russia to the United States in order to arrive before liftoff of the next shuttle mission.
- In 2012, a 16 kg shipment of cocaine was sent to the United Nations in New York in a bag masquerading as a diplomatic pouch.
- In January 2012, Italy detected 40 kilograms of cocaine smuggled in a diplomatic pouch from Ecuador, arresting five. Ecuador insisted it had inspected the shipment for drugs at the foreign ministry before it was sent to Milan.
- In November 2013, the UK government alleged that a British diplomatic bag had been opened by the Guardia Civil at the Gibraltar-Spanish border, sparking a formal diplomatic protest. The Spanish government responded that the bag, being transported from the Governor of Gibraltar by a courier company within a mailbag containing other packages, did not meet the criteria of being in transit between a diplomatic mission and a home government.
- Boczek, Boleslaw Adam (2005). International Law: A Dictionary. Scarecrow Press. pp. 51–52. ISBN 0-8108-5078-8.
- "Diplomatic bag: The inside story". BBC News. March 10, 2000. Retrieved 2008-10-05.
- "Vienna Convention on Diplomatic Relations 1961" (PDF). United Nations. Retrieved 2008-10-05., p. 8
- Javaid Rehman. Islamic State Practices, International Law and the Threat from Terrorism. Hart Publishing. Retrieved 2008-10-05.
- "Argentina's 1982 attempt on Gibraltar". Gibraltar Chronicle. December 28, 2012. Retrieved December 1, 2013.
- Rayner, Gordon (2009-10-16). "Yvonne Fletcher, Libya and betrayal of justice: timeline". The Daily Telegraph (London).
Rayner, Gordon; Hope, Christopher (2009-10-16). "WPc Yvonne Fletcher: 'We have guns and there will be fighting'". The Daily Telegraph (London).
"1984: Libyan embassy siege ends". BBC News. 1984-04-27.
- "Space Station Toilet Parts Set for Liftoff".
- Associated Press, Cocaine seized at UN in New York, 26 January 2012
- "UK protest at Gibraltar diplomatic bag opening". BBC News. 2013-11-26.
- Fiona Govan (27 November 2013). "Spain dismisses Gibraltar diplomatic bag incident". Daily Telegraph. Retrieved 4 December 2013.
- http://www.rtve.es/noticias/20131126/reino-unido-protesta-ante-espana-apertura-valija-diplomatica-gibraltar/802621.shtml (Spanish)