DUAL NATIONALITY in SPAIN (for US natives)...RENOUNCE US Citizenship?!

They are correct.  You have to formally relinquish your US citizenship at a US consulate or embassy via the proper forms in order to lose it.  See Afroyim v. Rusk (1967) and Vance v. Terrazas (1980).  It is true that according to USC Title 8 Section 1481 that obtaining naturalization in a foreign state (e.g. the Kingdom of Spain) is a POTENTIALLY expatriating act, the SCOTUS cases combined with US State Dept. administrative regulations and practice mean that you won't lose US citizenship unless you affirm on the proper forms (e.g. DS-4079) that you did indeed intent to lose/relinquish it by said naturalization.

IOW:  what the consulate told you was correct. 

Laws could always change in the future, but it seems to me an ex post facto law retrospectively stripping dual citizens of US citizenship won't hold muster.  In any case, you can always inform the consulate in writing that you explicitly do/did NOT intend to lose US citizenship by swearing in as a Spainard.  You will have to tell them this in any case, when you apply for a US passport renewal, as the form in question asks you if you have naturalized anywhere else.  This then could be a legal evidence for you later on in the unlikely case there is any question of your intentions.

LawLibrarian wrote:

You will have to tell them this in any case, when you apply for a US passport renewal, as the form in question asks you if you have naturalized anywhere else.  This then could be a legal evidence for you later on in the unlikely case there is any question of your intentions.

I was just looking at the passport application form and I don't see where you have to declare other nationalities.. where would they get this information from?

http://www.state.gov/documents/organization/212239.pdf?

Sorry I don't see it on this new form either--when I looked at one some years back, it was on the renewal form--along with a second question asking if you intended to relinquish/retain citizenship.  That it is not there today however is more evidence that DoS does have the administrative presumption in favour of people always intending to retain citizenship--i.e. they now don't even bother to ask you about other nationalities. 

Of course, some cynics might say this is because the government does not want citizens to expatriate, because then they would be released from legal obligations to file numerous IRS forms, and pay certain taxes where applicable and not covered by tax treaty with the foreign nation in question, even when living and earning (or investing/realizing capital gains (e.g. real estate, retirement funds, trusts)) abroad.  : )

I myself became Canadian and due to no real ties to the States anymore and no intention to move back ever, decided to relinquish US citizenship and had to fill out the forms at the consulate in Toronto.  They certainly did not know I had made any sort of loyalty oath to the Crown before I told them, unlike in the Vietnam era, when sometimes at least they had frowny-faced people at naturalization ceremonies looking for draft dodgers and dissidents who would get CLNs (Certificate of Loss of Nationality) mailed to them afterwards by Mr.Kissinger. 

See FAM 1254 Procedures b:  (this is what the guy at the consulate was looking at when he advised you):

http://www.state.gov/documents/organization/120544.pdf

ps. You likely already know this, but just in case you don't:  ALWAYS enter and leave the USA with your US passport, as required by law even if not always properly enforced at all.  Likewise, you should enter and leave Spain or any port of entry at an EU country with your Spanish/EU passport.  (i.e. carry both but only show the one at the proper respective port of entry).  The new DHS database system of keeping tabs on aliens entering the country has the potential for snagging dual citizens, QED:

http://www.alternet.org/story/153499/wh … deported_b

"More recently, an immigration detainer mistakenly snared Romy Campos, a 19-year-old American college student. Following a November 12 arrest for a minor misdemeanor, Campos was held in a California jail for four days and denied bail.

She was assigned a public defender in state court, but the attorney told her that nothing could be done to lift the federal detainer. Campos wasn't released until four days later when ACLU attorney Jennie Pasquarella provided ICE with Campos' Florida birth certificate.Campos is a dual citizen of the US and Spain and has both a US and Spanish passport, which she has used interchangeably. Because she once entered the US with her Spanish passport, she is recorded in the DHS database.

“I felt misused completely, I felt nonimportant, I just felt violated by my own country,”Campos toldtheTimes. While her detention was inexcusable, Campos is one of the luckier ones who got out quickly. Others have been detained for weeks and even months before proving their citizenship. "

LawLibrarian wrote:

ps. You likely already know this, but just in case you don't:  ALWAYS enter and leave the USA with your US passport, as required by law even if not always properly enforced at all.  Likewise, you should enter and leave Spain or any port of entry at an EU country with your Spanish/EU passport.  (i.e. carry both but only show the one at the proper respective port of entry).

if you were to try to enter the US with your non-US passport without filing that stupid 14 dollar pre-approval, do they even let you in? Although the lines are always some of the worst immigration wait times I've seen anywhere, it's also still slightly shorter to be in the US citizens line going into the States too.

not to mention that whole legality thing

what I don't understand though, is why the US has no exit inspection of passports. It always seems weird to me that they're so careful to check going in, but only do the ID check when departing.