This paper provides an ethical analysis of the controversy that arose from the CRISPR/Cas9 gene editing research involving human embryos that was conducted by a research team in Guangzhou, China, in 2015. It is argued that the researchers involved did not overstep ethical boundaries. This was confirmed to be the case in an international meeting of experts that was convened following the controversy. It is further argued that the controversy highlights the tension between two fundamentally different policies on developing genome editing technology – one proactionary and the other precautionary. This paper argues for a third approach, based on the policy of “crossing the river by probing stones”. Such an approach is consistent with current international recommendations to prioritise basic and pre-clinical research, and to allow the application of genome editing technology to somatic human cells. However, the application of the technology in germline genetic modification for human reproduction or enhancement for medical purposes should not be allowed at present. This is because the attending risks are not well understood and could be excessive or extraordinary, with little or no prospect of benefit. In addition, this paper calls for norms and regulations to be developed for genetically modifying non-human living things. Finally, the paper concludes with a letter that was sent by the author (and another) to the New York Times, setting out China’s fundamental stance on genetic modification involving humans and human derivatives.