Multiple citizenship was once an unacceptable situation, since - at times when countries had large-scale military service obligations and were regularly in conflict with each other - it was assumed that a person could have a relationship and corresponding loyalty only to one State. As US Attorney General Jeremiah Sullivan Black stated in 1859, "[N]o government would allow one of its subjects to divide his allegiance between it and another sovereign; for they all know that no man can serve two masters.” Theodore Roosevelt described the theory of multiple nationality as, “a self-evident absurdity.”
However, the increase of international marriages and family ties, increased migration, but also and in particular the professionalization of the military and the diminished relevance of compulsory military service in many States – one of the main problems arising from multiple citizenship – as well as a prolonged phase of general world peace since the Second World War, has meant that today, multiple citizenship is recognised or tolerated by an increasing number of States, and currently about half of all States allow, if not embrace, multiple citizenship. With this trend, gaining an additional citizenship and passport in an affluent and rule-of-law country no longer comes at the high cost of having to give up one's original citizenship: instead, you can have both.
The political attitude to multiple citizenship has also changed. While currently about half of the countries in the world allow multiple citizenship, every year more states follow in what seems an unstoppable trend: Belgium in 2010, Haiti in 2011, Niger in 2012, Sri Lanka in 2015, to name a few. Today multiple citizenship is valued for its potential capacity for international influence, as expressed by French Senator Joëlle Garriaud-Maylam, who declared: "The two and a half million French citizens living abroad, half of whom are bi-nationals, constitute a rich and varied network of entrepreneurs, project managers, importers and exporters, consultants and teachers who are indispensable to our external trade and our soft power."
Beyond migration, this global trend is driven by geopolitical, economic and technological factors. Fears over the loyalty of citizens - the main argument used against dual citizenship - faded after the Cold War ended and increased international political cooperation calmed international relations. Unlike earlier migrants in the 18th and 19th century, who had little contact with those they left behind them, 21st century migrants communicate with their families on a daily basis, by phone, internet, e-mail; they visit them for holidays; and return home for retirement. A new class of "global citizens" has furthermore emerged which truly have multiple homes and bases and for whom multiple citizenship is the norm. Yet multiple citizenship is still prohibited in many countries, and some only tolerate it in certain cases.
Viewed from the perspective of the individual, as “consumer citizenship” which is seen to flow from neo-liberal premises regarding the subjectivity of the new citizen, multiple citizenship reflects the commodification of citizenship itself, and instead of merely accumulating material goods, the global consumer citizen collects access rights: citizenships and passports. There are indeed many advantages for individuals to holding dual or multiple citizenships. The status is beneficial as it provides them with additional options: an alternative country in which to live and work (or, in the case of citizenship of any of the 28 European Union member countries, it means an additional 27 countries to choose from), an additional locus and source of rights and community ties, more visa-free travel and thus better personal mobility, and more personal security in the face of global terrorism directed very often at citizens of large, powerful countries such as the United States, the United Kingdom or Germany.
A person who has more than one citizenship is generally more privileged than a person with only one, and can in many cases freely chose the more advantageous of two passports, two legal systems and two or more places of residence.
With regard to citizenship granted in the national interest – such as Citizenship-by-Investment – it is actually desirable in most cases and also mostly unavoidable that the previous citizenship be retained. This has been recognised even in Austria, which generally still strictly requires the renunciation of previous citizenships as a condition of naturalisation, but in the case of naturalisation due to extraordinary contributions to the State - including economic contributions – it interestingly allows the retention of previous citizenships.
Multiple citizenship has undoubtedly eroded the strong bond between the individual citizens of a particular country and has led to the decoupling of citizenship status from the effective nationality. Having several citizenships means more options for the individual and a kind of citizenship of convenience: depending on the circumstances, one or another passport can achieve the objective best (e.g. no visa is required to travel, faster entry at border checkpoints for instance for EU citizens entering from outside of the EU etc.). This does not mean however that you cannot maintain a meaningful relationship with several states. Indeed, with increased mobility and the transnational lives of global citizens, having multiple ties in different countries and even on different continents has become much more commonplace and continues to increase worldwide.