Investment law is a branch of international law that deals with the rules and regulations governing foreign investment in a country. It aims to provide a framework for foreign investors to invest in a country while also protecting the rights and interests of both the investors and the host country. Investment law covers a range of issues such as expropriation, nationalization, dispute resolution, and investor-state arbitration. It is designed to promote and facilitate foreign investment by creating a stable and predictable legal environment for investors.