jats:pThis article relates to a set of recent reports about the Canadian Border Services Agency's (CBSA) use of commercial DNA ancestry tests to determine the nationality of detained migrants. While DNA tests are routinely used in many countries for the purposes of family reunification, these reports are particularly concerning. Not only do they imply a misunderstanding of the scope of genetics to shed light on legal and political phenomena such as nationality claims, but they also flag up important ethical problems regarding issues of consent and data privacy. In this article, the author clarifies the flawed logic behind using genetics to investigate nationality, outlines the ethical issues at stake and suggests amendments to existing norms in order to work towards more responsible practices in this area.</jats:p>