The only way of rescuing national sovereignty is by means of increasing supranational arrangements. It seems to me that this provides a bit more solid ground for the general insight of Fischer. In such a light, one should construct him as making a modest plea for constitution-making. After all, he is openly arguing for a federal Europe. The problem with federalism is that it means very different things to different people, and it is not always the case that everybody is eager to learn what others mean by it.
States can establish different frameworks of co-operation.
In a confederation, states retain their original sovereignty, while delegating a limited number of powers to the new central power, which is a mere creature of the states. In a federation, sovereignty moves to the centre, and states have their powers enshrined and limited in the federal constitution. However, one could doubt whether this mode of conceptualising sovereignty makes sense any longer. For one, Neil MacCormick has shown how the present structure of European law cannot be explained with such conceptual tools. The Union makes it clear that we have go beyond sovereignty.