Resumen.

Cross-border mobility of individuals has serious implications for states, irrespective of whether they are the emigration country or the immigration country and use citizenship or residence as the relevant criterion to exert their fiscal jurisdiction over the worldwide income of an individual taxpayer. This article illustrates in detail the various tax policies that a country can adopt to deal with cross-border mobility of individuals. The article first contrasts citizenship-based taxation with citizenship-by-investment programmes. Then, defensive strategies adopted by the emigration country against outward mobility of resident individuals are considered in parallel with preferential tax regimes for inward expatriates enacted by the immigration country. Next, the limited role - even after the Base Erosion and Profit Splitting (BEPS) Project - of tax treaties and other international tax instruments to curb competing fiscal policies of states is discussed. Finally, as a possible remedy to such clash of policies, the author tentatively proposes the abandonment of the long-established connecting factors of citizenship and residence and, in their place, the adoption of a new jurisdictional nexus based on the actual physical presence of an individual in the territory of a state, determined with the help of geo-localization technologies, which would lead to a proportional allocation of taxing rights among the countries interested in individual mobility.