Unilateralism and Conflict of Laws

For centuries, PIL has used unilateral and multilateral approaches. Each of them takes, as point of departure, a different conception of the aim and objectives of PIL, although, at the end, the results of unilateral and multilateral methods do not diverge essentially in the solution of many specific problems.Maybe we should considerer unilateralism and multilateralism as different tools, and for this reason, it would be necessary to focus in the practical use of each method instead relying on the essential differences of unilateral and multilateral PIL.Here we will discuss some of these issues, trying to understand the differences between unilateralism and multilateralism as two different phases in a two-steps PIL, but without leaving aside that these differences are also connected with changes of the political structures that have become lawmakers. As we are going to see, there is a connection between the decentralised political system during the Middle Ages and unilateralism; centralization of the political power in the 19th and 20th century and conflictualism; and the multilevel governance in Europe at the end of the 20th century and 21th century and the growing importance of unilateralism.