Citizens may engage with policy issues both to critique official justifications, and to make their own proposals and receive reasons why these are not favoured. Either direction of use can be supported by argumentation schemes based on formal models, which can be used to verify and generate arguments, assimilate objections etc. Previously we have explored the citizen critiquing a justification using an argumentation scheme based on Action-based Alternating Transition Systems. We now present a system that uses the same model to critique proposals from citizens. A prototype has been implemented in Prolog and we illustrate the ideas with code fragments and a running example.