Proportionality Expressing Local Visions of European Integration. European integration has relied on the idea of integration through law. Using domestic constitutional traditions as sources of inspiration, European courts have engaged different processes of integration according to the particular goals of supranational legal orders. Proportionality and the language of rights have played a major role in these processes. In Strasbourg case law, proportionality has been used as a principle of acculturation, which obliges national authorities to integrate common European constitutional values into domestic policy-making processes. In contrast, the kind of integration triggered by Luxembourg case law has traditionally focused on facts. It has consisted in the construction of a common market through the effective enforcement of EU market freedoms, sometimes to the detriment of other domestic values.