How can the concept of abuse of European Union law - which can be defined as undesirable choice of law artificially made by a private citizen - generate so much disagreement among equally intelligent individuals? Seeking to transcend the classical debate between its supporters and adversaries, the present study submits that the concept of abuse of EU law is located on three major fault-lines of EU law, which accounts for the well-established controversies in the field. The first fault-line, which is common to all legal orders, opposes legal congruence (the tendency to yield equitable legal outcomes) to legal certainty (the tendency to yield predictable legal outcomes). Partisans of legal congruence tend to advocate the prohibition of abuses of law, whereas partisans of legal certainty tend to oppose it. The second fault-line is specific to EU law and divides two conceptions of the regulation of the internal market. If economic integration is conceived as the promotion of cross-border c