In this chapter, there is an in-depth analysis of the case law on the concept of overlapping and the anti-overlapping rules. A series of cases is presented in order to show the interpretative approach of the Court and its impact on the anti-overlapping rules and thus pension rights. It is shown that the principle of favourability has been applied as a general and autonomous principle regardless Petroni principle from the namesake judgement which established the principle at issue. In fact, we criticise the reasoning of the Petroni judgment, as the Court did not apply its line of reasoning established in respect of Article 46 of the previous Coordination Regulation 1408/71. As we argue, the evolution of the anti-overlapping rules would be different if there had been a different direction in this crucial judgment. In the cases following Petroni, the Court sometimes reaffirmed and sometimes derogated from Petroni applying the principle of favourability independently from Petroni. Furthermore, the amendment of Article 46 of Regulation 1408/71 is presented in order to enlighten the different legal positions before and after Petroni which had as a consequence a strengthening of the anti-overlapping rules. As we argue, in its endeavour not to derogate from preventing any damage to the migrant, the Court ends with a precarious case-law. In the same context, the equal treatment of migrant and non-migrant pensioners is analysed.