Organising transport of nuclear substances presents a number of challenges, including how to properly qualify the substances from a nuclear liability perspective. The nuclear liability conventions provide a generic definition of “nuclear substances” (referred to as “nuclear material” under certain conventions), which gives wide discretion to national legislation in its interpretation. Moreover, the nuclear liability conventions also exclude certain categories of nuclear substances, subject to specific conditions being met, to ensure that the risk associated with their transport may be dealt with under general tort law. The implementation or application of these exclusions is carried out by each concerned country in accordance with its domestic legislation, which may lead to discrepancies in the qualification of substances to be transported by different stakeholders.