Article 296 TFEU

Where the Treaties do not specify the type of act to be adopted, the institutions shall select it on a caseby- case basis, in compliance with the applicable procedures and with the principle of proportionality.

Legal acts shall state the reasons on which they are based and shall refer to any proposals, initiatives, recommendations, requests or opinions required by the Treaties.

When considering draft legislative acts, the European Parliament and the Council shall refrain from adopting acts not provided for by the relevant legislative procedure in the area in question.