There is a wide-ranging debate about the merits and demerits of searching for, and sending messages to, extraterrestrial intelligences (SETI and METI). There is however reasonable (but not universal) consensus that replying to a message from an extraterrestrial intelligence should not be done unilaterally, without consultation with wider society and the rest of the world. But how should this consultation actually work? In this paper we discuss various ways that decision making in such a scenario could be done democratically, and gain legitimacy. In particular we consider a scientist-led response, a politician-led response, deciding a response using a referendum, and finally using citizens' assemblies. We present the results of a survey of a representative survey of 2,000 people in the UK on how they thought a response should best be determined, and finally discuss parallels to how the public is responding to scientific expertise in the COVID-19 Pandemic

11 pages, 2 figures, accepted Acta Astronautica