In countless ways we are affected by international environmental norms: some social, others legal; some quite general, others very specific. For example, the norms limiting the refrigerants used in air conditioners have been agreed upon in legal form internationally, and are mandated and enforced by national governments. The sustainable fishery and forestry standards used by Carrefour and Ikea were developed more informally by environmental groups and businesses, and are applied to producers through supply-chain contracts, without any government involvement. The reluctance to eat tuna fish or own elephant ivory reflects more general social norms, disseminated through education and culture.How and why do these norms arise? In what ways do they affect behavior? Do they change what states and individuals actually do and, if so, why? How effective are they in solving international environmental problems? In the second edition of The Art and Craft of International Environmental Law, Daniel
