The expression is misleading as it depicts something like a Sardinian criminal syndicate, similar to the Sicilian mafia, the Calabrian 'Ndrangheta or the Campanian Camorra.
Therefore, it is not correct to talk of a Sardinian criminal syndicate, since the Sardinian bandits responsible for the kidnappings lacked any kind of command structure, did not influence the political sphere, and several groups of bandits would operate with little to no relationship with each other.
The bandits, the most infamous of them being Graziano Mesina (also known as Gratzianeddu in Sardinian), Matteo Boe and Attilio Cubeddu (still one of the most wanted fugitives in Italy) to name a few, operated mainly in Sardinia but also in the nearby island of Corsica and, from the second post-war period onwards, decided to target the Italian peninsula, especially in regions where Sardinian immigrants already operated as shepherds.
Several writers have indicated an unwritten set of norms called "Barbagian Code" which was common to the rural and pastoral inner lands of Sardinia, these being the areas where most kidnappers originated, as well as those of hiding for most captivities.
The first documented kidnapping carried out in the contemporary era dates back to 1875 (the noblemen Antonio Meloni Gaia was kidnapped in Mamoiada in May 1875 in his vineyard, but managed to free himself and escape captivity later the same day),[2] while the unwritten code is assumed to have always existed in parallel to the written codes of the several foreign powers that ruled the island.