Chapter 4 assesses the history of companies in the international environmental law movement.Traditional voluntary-only approaches of industry groups to international environmental law led to a burgeoning of largely voluntary corporate social responsibility (CSR) initiatives. A review of the United Nations Framework Convention on Climate Change and the Kyoto Protocol are provided, along with a detailed examination of the Paris Agreement. Unlike previous experiences with international environmental law, many non-state actors supported the Paris Agreement, and some even wanted to become a party to it. While it remains a state-based treaty, non-state actors have become a main pillar of its implementation, particularly its long-term temperature goals. This international consensus shifting on climate change has led to new CSR and private environmental governance initiatives, specifically around climate change. These are eliciting a compliance reaction from many companies, with net-zero emissions targets announced by a variety of industry actors. Examples of Canadian Supreme Court decisions around corporate citizenship, the King IV Report from South Africa and CSR provisions in the Indian Companies Act 2013, as well as new corporate climate reporting requirements in the United Kingdom based on the recommendations of the Task Force on Climate-Related Financial Disclosures, are illustrative of this shift.