Recently a friend of mine that lives in Spain told me that he and his wife must renounce their citizenship if they want to be granted Spanish citizenship. This is confirmed by this article and by Wikipedia:

Spain permits dual citizenship under limited circumstances. Spain permits dual citizenship for all Spanish citizens by origin, so long as their declare their will to retain the Spanish nationality within 3 years of acquiring another nationality.

if a U.S. citizen acquires Spanish citizenship, Spain requires the person to renounce U.S. citizenship, but this is usually insufficient for the American to lose U.S. citizenship. In this scenario, Spain will view the person as solely a Spanish citizen, whereas the U.S. will still treat the individual as an American citizen. Practically, the individual will hold U.S. and Spanish dual citizenship.

Foreign nationals who acquire Spanish nationality must renounce their previous nationality, unless they are natural-born citizens of an Iberoamerican country, Andorra, the Philippines or Equatorial Guinea

I am wondering why Spain cares about having another citizenship. If I understood correctly it simply ignores the other citizenship in case of the US citizens.

Question: What is the rationale of not allowing dual citizenship?

  • 1
    I wonder if this question isn't a better fit for Expatriates.
    – ouflak
    Jul 3, 2019 at 6:22
  • 2
    I don't think this is necessarily true. I know US citizens who've acquired Spanish citizenship without losing their US status.
    – Obie 2.0
    Jul 3, 2019 at 8:15
  • 6
    @Obie2.0 - yes, this exception is covered by the first reference: Practically, the individual will hold U.S. and Spanish dual citizenship. which to me means something along: "we do not care if you are an US citizen, we will treat you as a Spanish one".
    – Alexei
    Jul 3, 2019 at 8:18
  • 2
    I'm not sure the article is saying that Spain ignores the citizenship of U.S. citizens. It seems more like Spain requires you to renounce your U.S. citizenship, but the U.S. requires more than just a statement to Spain to actually stop being a citizen.
    – RWW
    Jul 3, 2019 at 20:33
  • 2
    It’d avoid this crisis
    – Golden Cuy
    Jul 3, 2019 at 21:26

1 Answer 1


The rationale is to not dilute loyalty.

As an example, let's say person A has citizenship in both countries X and Y. Something happens, and X and Y go to war against each other, and they both conscript all eligible persons to fight in the war. Person A is eligible in both countries; which country will they betray?

  • 7
    If course it's rather more complicated than that in practice, but this is the basic underlying reason. +1
    – phoog
    Jul 4, 2019 at 1:46
  • 7
    They will lead the negotiations for peace, of course ;-)
    – gerrit
    Jul 4, 2019 at 13:53
  • @phoog an answer exploring the more complicated reasons would be extremely interesting
    – minseong
    Sep 27, 2021 at 20:47

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