Dual Nationality Codes

The traditional doctrine of absolute, singular state allegiance has steadily receded across international law over the last three decades. Once characterized by the 1963 Strasbourg Convention on the Reduction of Cases of Multiple Nationality as an anomaly to be suppressed, dual and multiple citizenship is now recognized by over eighty percent of sovereign nations as a lawful reflection of global human mobility.

The German StAG Overhaul: A Benchmark Shift

For decades, Section 10 of Germany’s Nationality Act (Staatsangehörigkeitsgesetz) mandated that naturalizing applicants must renounce their prior citizenship, subject only to narrowly construed hardship exceptions (such as exorbitant consular fees or refusal of permission by the origin state).

The legislative modernization passed by the Bundestag repealed this historic prohibition. Applicants acquiring German citizenship are no longer compelled to surrender existing nationalities, nor do German citizens who voluntarily naturalize abroad automatically forfeit their German status. This aligns German practice with other major European economies such as France, Italy, and the United Kingdom.

Persistent Prohibitory Regimes

Despite widespread liberalization, several influential legal jurisdictions strictly maintain singular nationality regimes. In nations such as Japan (under Article 14 of the Japanese Nationality Act), Singapore (under the Constitution of the Republic of Singapore), and the Netherlands (subject to distinct bilateral marriage exceptions), holding or acquiring foreign nationality triggers mandatory choice declarations or automatic involuntary loss of citizenship.

Legal Considerations: Military & Diplomatic Protection

Holding dual nationality carries nuanced consequences under international public law:

• The Master Nationality Rule: Rooted in Article 3 of the 1930 Hague Convention, a state may not provide diplomatic protection to one of its nationals against a state whose nationality such person also possesses.
• Military Obligations: Dual nationals may remain liable for compulsory national defense service unless bilateral accords, such as the European Convention on Consular Functions, grant military exemption based on habitual domicile.
• Taxation Compliance: Certain jurisdictions—most prominently the United States under the Internal Revenue Code—tax individuals on worldwide income purely on the basis of citizenship, regardless of physical residence.