There are two ways of becoming a citizen at birth: via jus sanguinas and/or jus soli. The first accords citizenship through a parent or grandparent and the second by birth within the border of a national territory. And if you think about it, that's just plain weird. Why is membership in the political and social community of a democratic nation-state conferred based on an accident of birth?
Furthermore, of the two methods, citizenship by blood is much less controversial than citizenship by place of birth. Most of us like the idea that this status passes from parent to child but to me that makes it look an awful lot like a hereditary aristocracy. Weren't there revolutions at one point over that?
Jus soli is a bit more inclusive and that's exactly why nations-states have used it. In the U.S. the Fourteenth Amendment resolved the issue of American citizenship for African-Americans and later on it was a very practical method for a young nation hungry for citizens to tie immigrant's children to the country of their birth as opposed to their parent's country. It is much easier to administer as well - in principle, under jus soli, all you need is a birth certificate to prove your citizenship. That is a lot cheaper and simpler than making folks come up a family tree every time they have to prove their status.
In France there was yet another benefit. In our time we have lost sight of the fact that residents of a country who don't have citizenship may have fewer rights but they also have fewer responsibilities. There are tales told of the French army going out into the villages to draft young men and discovering that some of the Frenchman were actually Italians or Spaniards (on paper at least) and thus could not be drafted. At that time military service could mean 7 years in the army and just imagine the anger of a French family when their sons were taken away and the neighbor's boys got off scot free. Well, they fixed that with something called double jus soli which means that a child born on French territory to a foreign parent who was also born in France was automatically a French citizen. Nice way to close the loophole, don't you think?
Both France and the U.S. confer citizenship using jus sanguinas and jus soli. What's interesting is that each country has different ways of using them to make new citizens. The U.S. has some restrictions on citizenship by blood for her citizens born abroad. These include residency requirement and whether or not the U.S. citizen parent is married (or not) and a father (or a mother). On the other hand, U.S. citizenship by jus soli as interpreted by the U.S. courts, is unconditional. If a child was born in the U.S. and left the day after his or her birth, he is a U.S. citizen and equal to all other U.S. citizens, until the day he or she renounced that status.
France does not have the same restrictions for jus sanguinas. A child born in France or abroad to a French citizen is a French citizen and it doesn't matter if it comes through the father or the mother or if they are married or not. However, France does not have unconditional jus soli like the U.S. There are requirements that must be met if a child born on French soil can become a French citizen or not. What are the conditions? Interestingly enough, it depends on the age of the child (or adult), when the request is made, and his or her residency on French soil.
So, for example, if a child of immigrants is 17 years old and wants to be French, she must have been born in France, living in France when the request is made and must have resided on the national territory for at least 5 years since the age of 11.
For those children of immigrants who are residing in France when they reach their majority (18), the conferral of French citizenship is automatic if they have lived on the national territory for at least 5 years since the age of 11.
To summarize, the U.S. has conditional jus sanguinas and unconditional jus soli citizenship laws. France is the exact opposite. That may be something of an oversimplification but overall, that's how it works.
I wrote this post in response to a comment that was left on one of my Path to Citizenship articles. The person commenting was asking about how to apply for French citizenship since he/she was born in France. His parents are not French, he/she said, but he didn't say where he was living or how many years he spent in France. Backing up a little bit, the first thing he needs to find out is if he's actually entitled to French citizenship at all because place of birth isn't enough. This site gives the criteria for all ages. If the answer is yes or he wants clarification of the conditions, the next step would be to contact the local French consulate if he's abroad or the local prefecture if he's in France and ask.
Citizenship laws are a source of endless fascination for me and France is a great country to study in this regard because just about everything has been tried. For a very good book about how French citizenship has evolved and changed over the last few centuries, I highly recommend Patrick Weil's
Qu'est-ce qu'un Français? Histoire de la nationalité française depuis la Révolution (available in English under the title, How to Be French: Nationality in the Making since 1789). Really good read, lots of fascinating research and you will never look at citizenship the same way again once you've reached the end of the book.
But be very careful - citizenship laws are a moving target. Countries make citizens and they can unmake them. Who knows what will happen in the future. Globalization and international immigration clearly strain the limits of the citizenship laws and models that have been passed along to us. What will the next generation of researchers make of the debates we are holding today? Once we were subjects and then, fairly recently, we were transformed into citizens. What, if anything, is next? I have no idea but I sure have an awful lot of fun thinking about it.