Soft law in the Paris Climate Agreement: strength or weakness?

In the lead-up to the Paris Agreement, and in reactions to it since its adoption, there has been a narrative which emphasizes the perceived advantages of key mitigation obligations in the Agreement being non-binding or ‘soft’ law. Central to these advantages is the idea that soft law obligations were a precondition for United States, China and wider participation in the Agreement, and also desirable in terms of flexibility. This article challenges the soft law narrative, arguing that the Paris Agreement's use of non-binding ‘nationally determined contributions’ has come at a cost in terms of likely effectiveness. Empirical studies comparing hard (binding) and soft law obligations in terms of compliance and effectiveness are equivocal, but precision of obligations and effective non-compliance mechanisms are essential. Moreover, when States have a strong political will to change behaviour, treaty instruments containing hard obligations have been considered to be more likely to be effective (e.g., ozone agreements, World Trade Organization agreements and arms control treaties). The development of the transparency, review and non-compliance elements of the Paris Agreement is essential, but is no substitute for strong political will to reduce emissions. In addition, it is crucial to muster the political will to ratchet up the Paris mitigation commitments and transform them from soft to hard obligations. The article assesses options for doing this, including a Conference of the Parties decision and a political declaration.