In addition to the Procurement Directives, a number of other sources of EU Law govern procurement and thus affect the manner in which GPP should be implemented.
The basic principles of free movement of goods, services, capital and people are set out in the Treaties*, along with a prohibition on discrimination based on nationality. From these basic principles a number of more specific principles applicable in the field of procurement have been developed, primarily through the case law of the European Court of Justice. These are the principles of transparency, equal treatment, proportionality and mutual recognition.
It is important to note that these principles are of broader application than the Directives - procedures which are excluded from or fall below the thresholds for application of the Directives must still be awarded in accordance with the principles. Public authorities need to observe these principles when implementing GPP, as in all areas of procurement.
* The Treaty on the Functioning of the European Union, the Treaty on the European Union and, formerly, the Treaty establishing the European Community.