As evidenced during the COVID-19 pandemic, there is a growing reliance on smartphone apps such as digital contact tracing apps and vaccination passports to respond to and mitigate public health threats. In light of the European Commission’s guidance, Member States currently offer such apps on a voluntary, ‘opt-in’ basis. In this paper, we question the extent to which the individual choice to use these apps – and similar future technologies – is indeed a voluntary one. By explicating ethical and legal considerations governing the choice situations surrounding the use of smartphone apps, specifically those related to negative consequences that declining the use of these apps may have (e.g., loss of opportunities, social exclusion, stigma), we argue that the projected downsides of refusal may in effect limit the liberty to decline for certain subpopulations. To mitigate these concerns, we recommend three categories of approaches that may be employed by governments to safeguard voluntariness.