This chapter examines the current situation concerning the codification, recognition, and implementation of corporate responsibility both in and outside the IIA regime, focusing on environmental and human rights responsibilities. It first discusses certain challenges in regulating and pursuing the responsibility of TNCs’ conduct in domestic legal orders. It proceeds to note a general lack of international mechanisms for holding TNCs responsible for their conduct, through the examination of: (a) the paucity of international law that provides binding obligations of juridical persons as well as a lack of enforcement mechanisms; (b) the attempts towards establishing binding international human rights obligations for corporations; and (c) the development of ‘soft-law’ instruments to advance the concept of corporate responsibility. The chapter then examines the recognition of investor responsibility in the text of IIAs and model IIAs by referencing a dataset of 1,000 randomly selected IIAs and model IIAs to confirm that incorporating the concept of investor responsibility into IIAs remains an exceptional practice.