When the Treaty of Rome established the common market in 1958, State intervention was a major feature of agriculture in the six founding Member States. The foundations of the common agricultural policy (CAP) have remained unchanged since then, with the exception of rules relating to the decision-making procedure.

The Lisbon Treaty recognised codecision as the ‘ordinary legislative procedure’ for the CAP, in place of the consultation procedure.
If the principle of the free movement of goods was to apply to agricultural produce, ongoing State intervention notwithstanding, national intervention mechanisms which were incompatible with the common market had to be transferred to Community level: this is the basic rationale behind the establishment of the CAP.