When a Swiss, U.S. or Chinese firm invests abroad, especially in emerging economies, what protection does it enjoy under international law? When countries, be they developed or developing, want to attract foreign investment to build up their infrastructure, exploit natural resources or transit to a green economy, what kinds of treaties can they adopt without endangering their regulatory autonomy or granting too much power to foreign multinationals? This course examines the public international law on the entry and protection of foreign investment both in customary international law and treaties, in particular bilateral investment treaties (BITs), free trade agreements (including NAFTA/USMCA, CETA and CPTPP) and the Energy Charter Treaty. It provides an overview of procedures for investor-state dispute settlement (ISDS) under arbitral facilities such as ICSID, elaborates on core substantive principles of FDI access and protection through an analysis of treaty provisions and the exponentially growing case law in the field, and assesses critiques of the ISDS system and ongoing treaty reform efforts. The course devotes attention also to the environmental and social issues surrounding foreign investment and efforts to regulate the obligations of multinational corporations. This is an overview course on the subject matter. No prior knowledge is required. Students in disciplines other than law are welcome.