Migration policy framework for Africa and plan of action (2018 – 2030) iv. Prosecution and Investigation zz Develop policies and guidelines on how to investigate and prosecute trafficking in persons, and provide training to relevant criminal justice officials such as police officers, prosecutors and judges. zz Establish specialised multi-disciplinary counter-trafficking law enforcement units or specialised prosecutors’ offices to effectively investigate and prosecute trafficking cases. zz Increase prosecution of traffickers and others involved in such activities, including through greater transnational cooperation, such as mutual legal assistance, and extend witness protection to trafficked persons who want to testify against traffickers. v. Partnership zz Increase the use of international cooperation when investigating and prosecuting cases of trafficking. zz Sign bilateral cooperation agreements in the fight against trafficking in persons supported by memoranda of understanding between States. zz Encourage cooperation among Member States and RECs to tackle human trafficking through the development and use of appropriate mechanisms, such as the Economic Community of West African States (ECOWAS) Model Bilateral Agreement on cooperation and mutual legal assistance in protecting children from transborder trafficking. 5.3 Return, readmission and reintegration A fundamental element of State sovereignty is the right of a State to decide who and under what conditions persons enter and stay in its territory. Return refers to the process of going back to a State, and can take place in different ways. Voluntary return can be assisted or independent, and takes place on the basis of the free will of the returnee. Readmission refers to forced return and occurs when an individual has been found to illegally enter or stay in a state. On the other hand, repatriation refers to the right of a refugee or a prisoner of war to return to his/her 54 country of nationality under specific conditions laid down in international law (Geneva Conventions, 1949 and Protocols, 1977, the Regulations Respecting the Laws and Customs of War on Land, Annexed to the Fourth Hague Convention, 1907, the human rights instruments as well as in customary international law). 19 Irregular migrants, especially those without documents, who need to return 19 IOM, 2004. Glossary on Migration