Non-Compliance Procedures are designed to facilitate the compliance of States parties with obligations deriving from Multilateral Environmental Agreements but may trigger harsher means to elicit compliance such as suspension of a party’s rights. The chapter will analyse the classical NCPs such as those in the Montreal Protocol on Substances That Deplete the Ozone Layer, the Convention on International Trade in Endangered Species of Wild Fauna and Flora, the Convention on Access to Information, Public Participation in Decision-making and Access to Justice in Environmental Matters and the Kyoto Protocol. It will then analyse the new type of NCPs, established in the Paris Agreement and the Rotterdam Convention on the Prior Informed Consent Procedure for Certain Hazardous Chemicals and Pesticides in International Trade and the Convention on the Protection and Use of Transboundary Watercourses and International Lakes. This chapter will analyse whether compliance is better ensured by more facilitative rather than coercive methods, together with NCPs’ legitimacy, including with reference to the powers of Conferences or Meetings of the Parties which mostly decide on non-compliance.