UN Being Sued by Human Rights Groups

In the context with our discussion about the independent legal personality of international organizations, and the extent to which they are subjects of international law, it was announced this week that a number of human rights groups have commenced legal proceedings in the courts of New York against the United Nations, for the role of U.N. Peacekeepers in causing the spread of Cholera in Haiti. How can such a law suite be brought against the U.N. in domestic courts? If the court takes jurisdiction, what would be the choice of law?