Many victims of FATCA, the US tax information collection law that requires international financial institutions to serve the US, have had negative experiences with the consequences of dual citizenship.

Apparently, it can be different (for those who are rich). In the article ‘Dual Nationals in Investment Treaty Arbitration: An Emerging Field of Inconsistent Decisions‘ by Javier García Olmedo, the author describes case law regarding investment treaties. From the introduction:

Nationality is a crucial marker for protection in international investment law. Only investors that qualify as nationals of a contracting party can access investment treaties. Most investment treaties, however, are premised on broad provisions defining eligible nationals. With respect to individuals, these instruments typically define protected investors as physical persons who hold the nationality of the home state party in accordance with its domestic laws.

He ends with the conclusion that claims by dual nationals is an emerging field within international investment law, that individuals are increasingly seizing opportunities that states have inadvertently created for them and that claims by dual nationals will continue to increase, and more awards will soon be rendered in pending cases.

I still don’t understand why nationality should be such an important criterion.