The making of the first global climate change agreement – COP21 – calls for some reflection over the status of public international law. Is this a binding treaty and it is law? There has been a huge debate about the differences and similarities between national law and public international law. Recently, legal scholars like Goldsmith and Posner have claimed that public international law is not binding and that governments can do what pleases them in terms of respect or non-respect for such law. In addition, professor Posner has argued that public international law is largely irrelevant in its humanitarian sectors, especially conventions about human rights. Yet, these claims are hardly tenable.