International law has never fully embraced multiple citizenship. Many countries frown on it, though others take a more relaxed attitude. Germany, however, manages to make it especially complicated for citizens of foreign origin. Its traditional approach goes back to a law passed before the first world war. Based on jus sanguinis (“right of blood”), it gave citizenship to anybody of German descent, but not to foreigners born in Germany, as countries such as America and France that practise jus soli (“right of soil”) do. Then, in 1999, a centre-left government added the two notions together. This would have let a woman born in Germany to Turkish parents be simultaneously German and Turkish. But that law coincided with a regional election in Hesse, where the centre-right Christian Democratic Union (CDU) seized on the issue to mobilise its conservative base in opposition. The CDU won the state and took control of the upper house, where it blocked the new law.
Emphasis added. While studying US immigration and citizenship law as a graduate student, the gender distinction surprised me. Why should male or female make any difference?
The answer to that question is culture. Women are not supposed to be geographically mobile. This bias is expressed in a number of ways from average commuting distance to international migration. Metaphorically, women are rooted to the soil, the earth of a nation. Men are free agents and should run off to sow their wild oats. Women more than men are stuck in captive labor markets. Those who are less able to move make less money.