In 2011 it was agreed to launch a new ad hoc Working Group on the Durban Platform for Enhanced Action (ADP) with a mandate “to develop a protocol, another legal instrument or an agreed outcome with legal force under the Convention applicable to all Parties.” The new negotiating process, which began in May 2012, is scheduled to end by 2015. The outcome should come into effect and be implemented from 2020 onwards. However, while the door is pushed open for formal discussion on questions of legal form, the choice of form is far from settled. The formulation in the ADP decision from Durban is marked by constructive ambiguity and requires further interpretation.This chapter begins with a discussion of the interpretation of the terminology in the Durban Platform on the legal character of a climate agreement. In the Next section we deal with the benefits of a legally binding agreement, with a particular focus on the binding character of the different elements of the agreement. Then we examine different approaches to differentiation between states in the agreement. Finally, we draw some conclusions about the substantive content and legal form of a future climate agreement.