They can be sued like anyone else, except for acts performed in connection with their official function. (No such exception applies to their family members.) ... Finally, no immunity applies to embassy employees (or the family members of such employees) who are nationals or permanent residents of the host country.

Can I sue immigration?

In short, yes. One can exercise their rights and legally sue USCIS. ... By filing a Federal lawsuit, you are forcing USCIS to justify their decision, which it is highly unlikely they will be able to do. In most cases where a Federal lawsuit has been filed, USCIS has chosen to avoid litigation and has issued an approval.

What is the doctrine of Nonreviewability?

“Consular non-reviewability” is a doctrine which renders unappealable in the US judicial system decisions made by US Embassy Consular Officers, regarding immigrant and non-immigrant visa applications.