Former fighters for the Islamic State are trying to return to their countries of origin. Germany is one country seeking ways to cancel passports. DW looks at how EU countries can strip citizens of their nationality.
The German government has just agreed to pave the way to strip former "Islamic State" fighters of their citizenship, while in the US and the UK, the "ISIS brides" Hoda Muthana and Shamima Begum have become household names for their public pleas to be allowed to return to their homelands.
Here's a look at how the involuntary loss of citizenship works across the EU.
Spain: No one born a Spanish citizen can be stripped of their citizenship against their will, per the Spanish Constitution. There are some statutes that stipulate that if a person becomes a dual citizen before the age of 18, they will lose their Spanish nationality within three years if they do not formally declare an intention to keep it.
France: In early 2016, still reeling from the terror attacks in Paris the previous November, the French government dropped a highly controversial plan to strip people with terrorist links of their passports and deport them. As it stands, in France only someone who becomes a citizen as an adult can have their nationality revoked. Unlike Spain, "disloyalty" and treason are grounds to take away citizenship.
Poland: Like in Spain, Poles who are citizens at birth can never have their nationality taken away. To renounce citizenship individuals have to make a personal application. Even then, each application must be personally approved by the president. Poland is one of only three EU countries, along with Sweden and Croatia, that does not cancel citizenships found to be obtained fraudulently.
Italy: For Italian dual nationals, it is relatively easy to give up Italian citizenship. To be involuntarily stripped of it, however, one must have "served" an enemy state, or fought for an army in active conflict with Italy. In this way, Italian law already provides for the annulment of nationality for foreign fighters.
Netherlands: The Netherlands and France are the only two EU countries that explicitly list terrorist activities as a reason to cancel a person's citizenship. Prolonged residence abroad can lead to involuntary loss of one's nationality, as can the acquisition of citizenship from another country.
Nine other countries take away citizenship after a long period of foreign residence. In Belgium, Denmark, Spain, and Sweden, however, this only applies to nationals who were born abroad.
According to the European Parliament statistics, in 15 EU countries, disloyalty can be given as a reason to strip citizenship. This can mean committing serious crimes against the state (the Netherlands, Belgium, Bulgaria and Denmark), acting against the constitutional order and national institutions (Denmark, Estonia, France, Latvia and Lithuania), "showing disloyalty by act or speech" (Cyprus, Malta and Ireland), or generally acting against national interests (France, Greece, Romania, Slovenia and the UK).