The aim of this article is to reexamine the ‘sovereignty’ argument used by many countries in support of their objection to ratify the International Convention on the Protection of the Rights of All Migrant Workers and Members of Their Families. Using a case study about the vulnerability of ‘trainees’ in Japan under its domestic labor policy, the Technical Intern training Programme, this article argues that the ‘sovereignty’ argument is no longer tenable, not only because policies and practices towards migrant workers have often contradicted the protection of rights guaranteed under the ICRMW, but also because the ‘sovereignty’ argument is nothing more than an excuse and a shield for human rights unfriendly domestic political economy. Therefore, a narrow conservative view that tends to contradict sovereignty and human rights needs to be reviewed as mutually complemented issues and a broader understanding of sovereignty that accommodates human rights is inevitable.