This course deals with the growing importance of international investment law. It will trace the traditional approach of regulating foreign direct investments in customary international law and then focus on the present state of investor protection through a dense web of more than 2000 bilateral investment protection treaties. The standards of treatment guaranteed to foreign investors in these treaties as well as under customary international law will be analyzed. Equally, the protection against expropriation will merit special attention. The growing case-law of international arbitration tribunals will serve as a background to this analysis.