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 entity. The physical concept of a "diplomatic bag" is flexible and therefore can take many forms. Additionally, a diplomatic bag usually has some form of lock and/or tamper-evident seal attached to it in order to deter or detect 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.
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 Louk was drugged, bound, and placed in a diplomatic mailing crate at the Egyptian Embassy in Rome, but was rescued by Italian authorities. The box that he had been sealed into "had almost certainly been used before for human cargo," including 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 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.