In contemporary positive law there are legal institutions, such as conscientious objection in the context of military service or "conscience clauses" in medical law, which for the sake of respect for judgments of conscience aim at restricting legal obligations. Such restrictions are postulated to protect human freedom in general. On the basis of Thomas Aquinas' philosophy, it shall be argued that human dignity, understood as the existential perfection of a human being based on special unity (individuality and particularity), provides a foundation for imposing limitations on the scope of legal obligations in general. Human freedom plays a crucial role in understanding dignity as perfection based on the special individuality of a personal being, which in turn is based on the free choice to pursue a unique way of life. Therefore, Aquinas’ argumentation is, at its core, liberal - the perfection rather than the imperfection of a human being underlies the requirement to limit legal obligations. Dignity understood as the special unity of a person also provides the basis for limiting obligations in the case of conscientious objection; however, in that case, such limitations aim at safeguarding internal integrity rather than the individualisation of a given way of life.