The chapter examines the evolution of the role of the home state in foreign investment law. Traditionally, such a role was essentially limited to norm-setting and protecting nationals and national companies abroad. Protection was typically offered through diplomatic protection, which was based on the legal fiction that the state was vindicating its own right. The conclusion of modern investment treaties, the progressive emancipation of foreign investors and the development of investor-state arbitration meant a marginalisation of the home state. Some recent treaties, however, have paved the way for a new role for the home state that goes well beyond protection of its nationals and national companies. Innovative provisions have introduced obligations and responsibilities for the home state, especially with regard to the fight against corruption and the liability of its own investors. It remains to be seen to which extent these provisions will spread across the international community of states.