18.—(1) These Regulations do not apply to procurement for the award of a public contract or to a design contest involving defence or security aspects which the contracting authority is obliged to award or organise in accordance with procurement procedures which are established by—
(a)an international agreement or arrangement, concluded in conformity with the Treaties, between the United Kingdom and one or more third country or part thereof and covering works, supplies or services intended for the joint implementation or exploitation of a project by their signatories;
(b)an international agreement or arrangement relating to the stationing of troops and concerning the undertakings of the United Kingdom or a third country; or
(c)an international organisation.
(2) These Regulations do not apply to procurement for the award of a public contract or to the organisation of a design contest involving defence or security aspects which the contracting authority carries out in accordance with procurement rules provided by an international organisation or international financing institution where the public contract or design contest concerned is fully financed by that organisation or institution or is co-financed for the most part by such organisation or institution.