This Directive shall not apply to contracts governed by:

(a) specific procedural rules pursuant to an international agreement or arrangement concluded between one or more Member States and one or more third countries;

(b) specific procedural rules pursuant to a concluded international agreement or arrangement relating to the stationing of troops and concerning the undertakings of a Member State or a third country;

(c) specific procedural rules of an international organisation purchasing for its purposes, or to contracts which must be awarded by a Member State in accordance with those rules.