The case of the day is Moskovits v. Brazil (S.D.N.Y. 2021). Alexander Moskovitz, an American/Brazilian dual national residing in Brazil, claimed that he had worked for Calvin Grigsby, an agent of Bank of America, who had brokered $2 billion in “unprecedented transactions” between the Bank and several Brazilian states. The claim was that he had not been compensated for his work because he had “refused to participate in closing any transaction through foreign corrupt practices.” Moskovits, acting pro se, sued Brazil, three Brazilian states, and two Brazilian individuals. The district court dismissed the case on the grounds that because Moskovits was a US citizen domiciled abroad, there was no diversity of citizenship and the court lacked subject matter jurisdiction.
There is indeed a rule that says that a federal court does not have diversity jurisdiction when one of the parties is a US citizen domiciled abroad, because he is not an alien, and also not a citizen of any of the US states. But diversity of citizenship is not a basis of any lawsuit against a foreign state. The FSIA is the only basis for asserting subject matter jurisdiction over a foreign state. Moskovits sought reconsideration, and the court granted it.
I mention the case as an illustration of why acting pro se is a bad idea. The complaint here was not terrible, but the jurisdiction section spends a lot of time talking about the dollar amount of the damages, which probably misled the court in the first instance, because amount in controversy is a factor in diversity jurisdiction. But even if there were no drafting issues, suing a foreign sovereign has many more pitfalls than a typical lawsuit. “Do it yourself” is not a good strategy in these cases.