Germany is one of the few countries in the world that still primarily bases its citizenship on "blood". It harks back to a law passed in 1913 during the Imperial Period. The application of this law spurs many irregularities. For example, immigrants from Romania, Poland or the Russian Federation who cannot speak a word of German, who've never seen Germany, and who are completely un-German culturally, can arrive in Deutschland and automatically lay claim to citizenship because their ancestral forbears emigrated from a German province some centuries earlier. On the other hand a Turk, Croat, or Italian, born and raised in Germany, who speaks fluent German, and who has never seen his ancestor's homeland, is not quite a full German citizen. They have a limited dual-citizenship that requires them to choose one allegiance and renounce the other before their 23rd birthday.