Under international law, the state's sovereign power to expulse migrants in an irregular situation is broad yet not absolute. International human rights law lays down several obligations which circumscribe state's prerogatives in the context of expulsion. The overarching human rights framework applicable in the context of expulsion builds upon states' obligations flowing from the principle of non-refoulement, the right to life, the prohibition of torture and ill-treatment, the prohibition of arbitrary detention, the prohibition of collective expulsion, the right to respect for family and private life, the right to effective remedy, and the right to access basic social services. On that premise, the thesis undertakes a rigorous human rights assessment of the European Union (EU) Directive 2008/115/EC of the European Parliament and of the Council of 16 December 2008 on common standards and procedures in Member States for returning illegally staying third-country nationals (Returns Directive), which governs the EU returns policy. The thesis examines the main measures spelled out in the Directive, such as return, re-entry ban, immigration detention, and removal, against the relevant human rights norms and standards. Based on this assessment, this thesis discusses several protection gaps in the Directive's provisions which may result in human rights violations. Since the compliance with EU law does not relieve the EU member states from their international obligations, states should complement the Directive's rules with more protective standards stemming from their human rights obligations.