French nationality law is historically base on the principle of jus soli, according to Ernest Renan's definition, opposed to the German's definition of nationality formalized by Fichte. However, elements of jus sanguinis have been included in the French code, especially during the 1992 reform, which forced children born in France of foreign parents to request French nationality at adulthood, instead of being automatically accorded it (no conditions are required to acquire it, but it forces children of foreigners to go through a bureaucratic process, while children of French citizens - whether immigrants or not - cut through all the red tape). As in most other countries, but differing from the US, children born in France to tourists or short term visitors do not acquire French citizenship by virtue of birth in France: residency must be proven. As immigration became more and more of a political theme in the 1980s, albeit a lower immigration rate (see Demographics in France), both left- and right-wing governments have issued several laws restricting more and more the possibilities of being naturalized.