The fundamental problem with the sovereignty-preserving approach is
that transnational tax bases are not givens that sit still andwait to be carved
up between national tax authorities: rather, tax bases are endogenous to
the rules themselves. Taxpayers, individual and corporate, can structure
their cross-border activities in such away that – given the regime’s sharing
rules – they can minimize their tax payments. While many of the decisions
to abandon capital controls, lower trade barriers and other policies of liberalization
that enhance the international mobility of tax bases were taken
outside the tax treaty regime, this is only a necessary but not sufficient
condition for under-taxation. The possibilities for tax evasion and avoidance
arise only in combination with the sovereignty-preserving design of
the institutions of double tax avoidance. The DTA regime provides the
institutional foundation of tax competition.