Citizenship laws provide for a variety of grounds for the involuntary loss of citizenship. The most important of these are: maintaining residence abroad, voluntarily acquiring another citizenship, taking up service in a foreign army or rendering services to foreign countries, committing acts of disloyalty or treason, and acquiring citizenship fraudulently.
All EU countries, except for Croatia, Poland and Sweden, provide for the withdrawal of citizenship in cases of discovered fraud in the acquisition of citizenship (see Figure 5). In 12 EU countries, persons can be deprived of citizenship if they take service in a foreign army. Prolonged residence abroad is grounds for the involuntary loss of citizenship in 10 EU countries. However, in Cyprus, Ireland and Malta, this applies only to naturalised citizens, whereas in Belgium, Denmark, Spain and Sweden it only concerns citizens who were born abroad. The acquisition of another citizenship can lead to the withdrawal of citizenship in nine EU countries: Austria, Estonia, Germany, Ireland, Latvia, Lithuania, the Netherlands, Slovakia and Spain.