Abstract Especially solidarity has often been referred to in the context of the Euro-crisis, yet it has not played a very pronounced role in case law or secondary law. This article shows that instead of determining the legality of Union measures to address the Euro-crisis, both solidarity and loyalty had an enabling function for Member State measures outside of the Union framework. After Pringle and the addition of Article 136(3) TFEU, at least in the EMU positive (financial) solidarity has taken on a conditional form, offsetting the conflict that would otherwise exist with the fiscal discipline required by primary law. Loyalty underpins the independence of the ECB, both in substantive terms as well as in organisational terms. Both solidarity and loyalty finally converge as foundations of the rule of law in the Union, which is important with regard to the sanctioning mechanisms in the EMU.