>Then I don't understand the question. Citizenship is a legal status.

Depends on the culture.

In ancient Athens, for example, being a citizen was attached to a moral imperative towards your state, not just a mere "legal status".

You were first and foremost a citizen. In fact the opposite, a person concerned with his own affairs first and foremost, was considered by the culture an inferior person, and the word use ("idiotis" -- literary "private/concerned with private affairs"), survives to english as "idiot".

That wasn't the case only in ancient Greece of course. In all kinds of cultures, citizenship and being a citizen, was considered as something bigger than "i got this legal stamp".

By the way, I always thought that "Starship Troopers" were basically ancient Greece replayed in sci-fi setting. In Greece all citizens had to fight for the state, when the need arises (which was happening regularly and the threats were very serious). Sometimes they conscripted slaves, but the slaves were given freedom (or maybe even citizenship) after that.