122 Swider and den Heijer Our second set of arguments is comprised of EU rationales for harmonization. First, approximating rights of entry and residence of third-country nationals and stateless persons, as well as the standard of treatment to be accorded to them, is an objective of the Union and laid down in Article 79 TFEU. The rationale of this objective is that in a Union area without internal frontiers, disparities in the treatment of third-country nationals (and stateless persons) may result in undesirable ‘push’ and ‘pull’ effects which cannot be effectively controlled due to the absence of internal border controls. This rationale includes taking measures to preclude the so-called ‘race to the bottom’ effect. The experience with establishing the Common European Asylum System shows that a protection regime for vulnerable groups in the EU needs to be coordinated on the EU level to avoid dynamics by which stateless persons will choose to seek protection in the Member State which they consider most attractive. To counter that effect, Member States may not only feel reluctant to increase their level of protection but may indeed be tempted to decrease their relative attractiveness compared to other Member States, potentially prompting a race to the bottom and resulting in an overall lowering of the level of protection across the EU. There is no evidence whether any significant numbers of stateless persons actually engage in such a ‘forumshopping’ behaviour, and whether that behaviour influences the policies of individual Member States. However, in the context of open borders, it is the EU’s responsibility to ensure that such considerations do not play a role in domestic decision-making. Member States which strive to comply with their international obligations on statelessness should not be hindered by fears of attracting disproportionate numbers of stateless persons from other Member States. Similar to the reasons advanced for establishing a common European asylum policy, therefore, the rationale for EU action on statelessness would be to create a level legal playing field, which prevents forum-shopping and ensures in all Member States a minimum level of protection in accordance with international obligations.85 Further, the need for well-functioning procedures through which statelessness can be determined is already implied in existing EU law. Since EU law treats stateless persons as third-country nationals (Art. 67(2) TFEU), such persons fall within the personal scope of all EU legislative instruments on migration, such as the EU asylum directives, the Family Reunification Directive (2003/86/ EC), and the Return Directive (2008/115/EC). Insofar as national procedures 85 Cf. the rationales for establishing a Common European Asylum System as formulated in the Tampere Programme, Conclusion of the European Council of 15/16 October 1999. European Journal of Migration and Law 19 (2017) 101–135