Abstract
MFN provisions in investment agreements have been a tool for equitable treatment between foreign investors with different nationalities. This non discriminatory principle has been pursued by the host states for further investment promotion. However, it may be abused to bring the situation of so called "ISDS forum shopping" which might harm the stability and predictability of investment agreements by unexpectedly extending the scope of obligations. While some investment arbitral tribunals have interpreted the scope of MFN provision very broadly to allow the ISDS forum shopping, both procedural and substantive provisions have been invoked. To prevent any chaos of unclear boundary of MFN provision, some explicit MFN restrictions which would limit the scope of MFN provision are needed. Indeed, some investment agreements have included these MFN restrictions. Specifically, MFN restrictions deal with both procedural or substantive provisions to prevent ISDS forum shopping. According to the lessons from the recent examples of MFN restrictions, there must be a careful consideration on the benefits and costs of having a certain type of MFN restriction as the parties can be the host state and the home state of their investors at the same time.