What are these Latin words doing on my Italian blog? OK, the Italians are the descendants of the ancient Romans, but they're not really ancient Romans (no matter what some of them may think). But like us, they evidently got much of their judicial infrastructure from the Romans.
These ancient words are actually quite topical, both in Italy and the US. What they refer to is no less than the basis of someone's national identity. Jus soli is literally the law of the soil: the basis of citizenship is the land, that is, where one was born, for whatever reason. With jus sanguinis (literally, law of blood), citizenship is determined by "blood," that is, ethnicity or kinship.
For obvious reasons, the US, which started as a new country with a heterogeneous population, adopted the law of the soil, so that you are an American if you were born here, even if your mom got here the day before. Italy, which is an old country with a homogeneous population, uses the law of blood, so that you are Italian if you are ethnically Italian. I, for example, although born in the US from an American father, am eligible for Italian citizenship because I have two Italian grandparents and my Italian-citizen mother was a citizen when I was born. Italians do in fact consider me Italian, and merely specify that I was born in America, as if it were some sort of accident (or misadventure).
These are over-simplifications, of course. But it should come as no surprise that our rapidly (too rapidly) globalizing world is making these categories hard to sustain. At this time in history, many Americans are questioning the law of the soil because of abuses by immigrants (often illegal) who seek a foothold here by having children. Some are seeking repeal of the birthright clause of the Fourteenth Amendment. Ironically, some Italians are now questioning the law of blood, due to the high numbers of assimilated immigrants (many of them of color and many of them born in Italy). Widely-respected President Giorgio Napolitano has recently called for a repeal of the law of blood.
These seem to be theoretical, legalistic matters, but they are of practical importance to millions throughout the world, and may well define the nature of our world in the decades to come. A human face can be put on the question by the story of superstar soccer player Mario Balotelli, a (very) black young man born in Italy to Ghanaian parents, and later taken into foster care by Italians. He is now a citizen. The 21-year-old has confronted considerable anguish in his short career by Italians harassing him at the stadium and online with racists taunts and asserting that you can't be black and Italian. He now plays in England.
Above you see a video put out by ARCI, a left-leaning organization that supports Napolitano's position on birthright citizenship in Italy. It provides a timeline of the life of young Davide, born in Italy and doing all the Italian stuff, liking riding a Vespa as a teen. It then shows that when he comes of age he is brutally informed that he is not Italian and he has 12 months to show that he is.