The externalization of migration control undermines the protection of victims of trafficking in human beings. Pushbacks and pullbacks at sea, as well as simplified or accelerated identification procedures, exacerbate the risk of trafficking and retrafficking and prevent victims from accessing the protection to which they may be entitled in European States. In this scenario, the European Court of Human Rights can play a crucial role among international bodies and courts in ensuring effective remedies for victims in case of repatriation to their countries of origin and transit. This study examines the applicability of the prohibition of slavery, servitude and forced labour enshrined in Article 4 of the European Convention on Human Rights—whose scope now undisputedly includes trafficking in human beings—in the context of the externalization of migration control. It demonstrates that litigating unlawful refoulements under Article 4 ECHR might be very worthwhile to raise awareness of migration-related risks for victims, to strengthen the legal framework of positive obligations in trafficking cases, and to ascertain violations of anti-trafficking international obligations by European States.