The Exclusive Citizenship Act and the Future of Dual Nationality in America

A proposed U.S. law seeks to eliminate dual citizenship entirely, placing it in direct conflict with global legal trends and constitutional precedent.

“Allegiance to the United States must be undivided.”

So declares the Exclusive Citizenship Act of 2025, introduced by Senator Bernie Moreno. The bill is striking for its bluntness: if enacted, U.S. citizens holding another nationality would have one year to renounce their foreign citizenship or forfeit their American citizenship.

Global Trends in Dual Citizenship

Yet what makes the proposal remarkable is not its directness but how sharply it runs against the global trend. Over the past sixty years, the proportion of countries permitting dual nationality has risen dramatically, from roughly 38% in the 1960s to more than 75% today. The liberalisation has been unmistakable. The reverse – countries shifting from permitting dual nationality to prohibiting it – is exceptionally rare.

Several clear examples exist, including the nationality regimes of the Netherlands following its 1984 Nationality Act, the People’s Republic of China under its 1980 nationality law, and Slovakia after its 2010 amendment imposing loss of citizenship upon voluntary naturalisation abroad. But even in such cases, the mechanisms used were typically prospective. Rather than forcing existing dual nationals to choose between citizenships, governments generally introduced rules under which citizenship could be lost if a citizen voluntarily acquired another nationality. The existing stock of dual citizens was almost always left untouched.

The Exclusive Citizenship Act is therefore highly unusual not only in its objective but also in its mechanism. Rather than simply preventing future cases of dual nationality, it would attempt to eliminate the millions of dual citizens who already exist.

The Scale of Dual Citizenship in the United States

The scale of the issue is often overlooked. Around 9 million U.S. citizens currently live outside the United States, many of whom maintain deep personal, professional, and family ties across borders. Within the United States itself, roughly 23 million Americans are naturalised citizens, having been born in another country and later acquiring U.S. citizenship. Each year, hundreds of thousands of immigrants continue to join that group. According to the U.S. Citizenship and Immigration Services, more than 800,000 people naturalised as U.S. citizens in fiscal year 2024 alone, and annual totals have frequently approached one million in recent years. Many of these new citizens retain their original nationality where their home country permits it.

At the same time, large numbers of children are born in the United States to parents who hold foreign citizenship. Under the nationality laws of many countries, these children automatically inherit their parents’ citizenship whilst also acquiring U.S. citizenship at birth. Taken together, these dynamics mean that millions of Americans already possess another nationality, and hundreds of thousands of new dual citizens arise each year as a routine consequence of immigration and birth.

Any attempt to eliminate dual citizenship would therefore require forcing millions of existing American citizens to renounce another nationality or lose their U.S. citizenship – an undertaking for which there is virtually no precedent in modern nationality law.

The Constitutional Constraint on Restricting US Dual Citizenship

There is also a significant constitutional obstacle.

In Afroyim v. Rusk (1967), the Supreme Court held that Congress cannot involuntarily strip a person of U.S. citizenship. The Court concluded that the Fourteenth Amendment protects citizenship from congressional revocation unless the citizen voluntarily relinquishes it.

Subsequent decisions reinforced this principle. In Vance v. Terrazas (1980), the Court held that loss of citizenship requires proof of an individual’s intent to relinquish nationality, not merely the voluntary commission of an expatriating act such as voting in a foreign election or acquiring another citizenship.

This jurisprudence raises serious questions about whether legislation compelling citizens to choose between nationalities could withstand constitutional scrutiny.

How Restrictions on US Dual Citizenship Could Work in Practice

If the United States were to seriously attempt to restrict dual nationality, the most plausible model would resemble the mechanisms used by countries that already limit it.

Rather than requiring millions of existing dual nationals to choose between citizenships, Congress could attach consequences to future voluntary conduct. For example, legislation might provide that a U.S. citizen who voluntarily naturalises in another country is presumed to have relinquished U.S. citizenship.

Such a rule would likely operate prospectively rather than retroactively, tying potential loss of citizenship to voluntary conduct and aligning more closely with the constitutional doctrine developed in Afroyim and later clarified in Terrazas.

Implications for US Citizens Considering Second Citizenship

If enacted in its current form, the Exclusive Citizenship Act would represent one of the most ambitious attempts by a democratic state to eliminate dual nationality in modern history.

It would, however, confront two powerful constraints.

The first is legal. American constitutional law treats citizenship as a status that cannot be involuntarily taken away by the government.

The second is structural. Dual nationality has become deeply embedded in the fabric of American citizenship through immigration, international mobility, and the interaction of global nationality laws.

For Americans considering acquiring a second citizenship or Citizenship by Investment, the lesson from comparative experience is straightforward: when states do tighten citizenship rules, however rare such restrictions might be, they almost always do so prospectively, applying new restrictions to future conduct rather than retroactively stripping existing rights.

The legal environment today cannot necessarily be assumed to remain unchanged. But once a second citizenship has been lawfully acquired, it is extremely difficult for democratic states to take it away after the fact.

To discover more about your Citizenship by Investment solutions, please do not hesitate to get in touch with our experts.

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