[MsDemeanor]

It's actually kind of interesting. There are two widely recognized methods of determining citizenship - jus soli (right of the soil) and jus sanquinis (right of the blood). In the Americas, jus soli seems to be prevalent, which makes sense in a large land mass surrounded by oceans that contains folks who predominantly came from somewhere else. European countries tend to use jus sanquinis, which, to me, makes more sense the goal of preserving national heritage in a region with a lot of little countries with free movement between them. If your parents are Spanish, you're Spanish, even if you're born in France. There's also lex sanquinis, which allows citizenship based on other blood ties. For example, if my great grandparents had my grandmother before they left Ireland, rather than after they arrived in the States, I could get an Irish passport (stomps foot), and the Israeli Law of Return grants the right to citizenship to all Jews.