Investor–state dispute settlement (ISDS), or an investment court system (ICS), is a set of rules through which states (sovereign nations) can be sued by foreign investors for certain state actions affecting the foreign direct investments (FDI) of that investor. This most often takes the form of international arbitration between the foreign investor and the state. As of June 2024, over US$113 billion has been paid by states to investors under ISDS, the vast majority of the money going to fossil fuel interests.
ISDS most often is an instrument of public international law, granting private parties (the foreign investors) the right to sue a state in a forum other than that state's domestic courts. Investors are granted this right through international investment agreements between the investor's home state and the host state. Such agreements can be found in bilateral investment treaties (BITs), international trade treaties such as the 2019 United States–Mexico–Canada Agreement, or other treaties like the 1991 Energy Charter Treaty.