Providing proof of legal identity to those without existing documents The Agenda for Sustainable Development and its SDGs, adopted by consensus resolution of the UN General Assembly in 2015, established the overall commitment of the global community to “leave no one behind” in access to the benefits of development. Considering the impact of this commitment on the implementation of identification initiatives, there are at least three possible approaches to the issue of a document (or other identity token confirming registration) that would enable people currently lacking the required identity documents to access rights and essential services. Functional identity The first approach is to provide access to services on the basis of a “functional ID” specific to each task, whether issued locally (e.g., a health clinic card issued to anyone using the service), or nationally (e.g., registers maintained for elections, driving licenses, tax payment, or food rations). Functional identity systems have been commonly used historically, especially—but not only—in countries without a national identity register, or where enrollment in a national identity register is very incomplete. Central registration without proof of legal status The second approach is to register all those born or resident in a territory without distinction, and accept that registration as proof of identity and permission to access at least basic rights and services, without additional proof of nationality or legal immigration status. This form of registration is the model for most birth registration systems, supported by decades of work by UN agencies (notably UNICEF and UNSTATS) and by SDG 16.9, “to provide legal identity for all, including birth registration.” This approach was also the original vision for India’s Aadhaar biometric registration system, which inspired a number of other new systems in nations where historical rates of birth registration have been very low (for example, Nigeria and Ethiopia).17 This approach avoids the cost of repeat registration in different systems required by the use of multiple types of functional ID, as well as the challenges of determining legal status in the context of low rates of existing documentation. It also has an appealing simplicity compared to traditional civil registration systems. Biometric registration provides the robust proof of uniqueness necessary for the digital economy and desirable for tasks such as deduplication of benefit recipients. 17 Pilling, “India Points the Way to Digital Access across Africa.” Statelessness and digital identity 7