In the context of the current negotiations of the Ad Hoc Durban Platform for a new global agreement on climate change, discussions are in progress concerning the legal form of this agreement. In particular, deliberations are underway regarding norms that would be legally binding internationally, and norms that would be legally binding domestically. An international obligation to pass and to implement domestic climate legislation would combine these two dimensions. This paper sees the basis for this idea in the no harm principle of international environmental law, stemming from the Rio Declaration on Environment and Development of 12 August 1992, and incorporated into the United Nations Framework Convention on Climate Change (UNFCCC). Similar concepts exist in other areas of international law, such as human rights, humanitarian law, and diplomatic relations, reflected by the notions of due diligence and of responsibility to protect. In addition to obligations of result, the possible added value of obligations of conduct to pass and implement domestic climate legislation for mitigation, adaptation and means of implementation is analysed. Concerning mitigation in particular, it is important to understand the specific features of such obligations compared to the obligations of result contained in the Kyoto Protocol.