Since Russell and Burch introduced and defined the 3Rs, i.e., the replacement, reduction, and refinement of animal use in research, in 1959, different definitions have emerged and been implemented in guidelines and policies. Switzerland is known for having some of the most restrictive legislation regarding the use of animals, in which the 3Rs are also defined and implemented. To our knowledge, the purpose and definitions of the 3Rs used in the Swiss Animal Welfare Act, Animal Protection Ordinance and Animal Experimentation Ordinance have never been compared with Russell and Burch’s original purpose and definitions. In this paper we make this comparison with two aims: to reveal ethically relevant departures from the original purpose and definitions, and to provide an ethical evaluation of the current Swiss law regarding the 3Rs. In doing so, we first expose the similarity of purposes. We then identify one risky departure from the original definition of replacement in Swiss law, which shows a problematic focus on species. Finally, we address Swiss law’s failure to apply the 3Rs in the most effective way. With respect to this last point, we discuss the need for 3R conflict resolution, the timing of application of the 3Rs, problematic prioritizations and choices of convenience as well as a solution to apply the 3Rs more effectively using Russell and Burch’s concept of total sum of distress.