Let’s say I become a citizen of a country that doesn’t allow dual citizenship. During naturalization, new country B tells me I have to renounce citizenship from old country A.
Does that have any effects back in country A? How would country A know? Would country A even care if they found out?
It’s very difficult to enforce. I’ve heard of cases where people like show the embassy a passport of a citizenship they said they renounced by accident, and were just sternly told to renounce it, other cases where their new citizenship was revoked.