In January 2010, Mexico City added articles 1796 Bis and 1796 Ter to its Civil Code. They introduced the teoría de la imprevisión, the doctrine of the unforeseeable event. When an extraordinary and unforeseeable event upsets the conditions of a contract, a party “tiene derecho de pedir la modificación del contrato,” has the right to ask for the contract to be changed.
The request does not by itself allow the party to stop performing. The party who asks for the change may go to a judge to settle the dispute. A change does not apply to what was delivered before the event. According to a UNAM law journal, twelve states, among them Jalisco, the State of Mexico and Veracruz, already had the doctrine.