I am currently a Colombian citizen with a US residence. My US green card was issued in March 2005, from my understanding I can apply for US citizenship 90 days before March 2010.
My grandfather was from Spain and there is a new law that grants Spaniard citizenship to grandsons if they can prove that their grandfather was from Spain. In Colombia if you can prove that any of your parents is from Spain you can get the citizenship, now my grandfather passed away and my father passed away before he could apply for a citizenship from Spain. My uncles (my fathers brothers) have applied for the Spaniard citizenship and it has been granted and their daughters and sons have applied thereafter and also been granted citizenship.
My questions is; I will be applying for my US citizenship in November of 2009, I am also interested in getting the European citizenship thru Spain, I know that at some point I will have to renounce to my Colombian citizenship, would me applying for the citizenship in Spain affect my US citizenship?
Is there a law against dual citizenship in the US?
Thanks.

