It is a common place of academic and political discourse that the EC/EU, being neither a parliamentary democracy nor a separation-of-powers system, must be a sui generis polity. Tocqueville reminds us that the pool of original and historically tested constitutional models is fairly limited. But however limited, it contains more than the two systems of rule found among today's democratic nation states. During the three centuries preceding the rise of monarchical absolutism in Europe, the prevalent constitutional arrangement was ‘mixed government’—a system characterised by the presence in the legislature of the territorial rulers and of the ‘estates’ representing the main social and political interests in the polity. This paper argues that this model is applicable to the EC, as shown by the isomorphism of the central tenets of the mixed polity and the three basic Community principles: institutional balance, institutional autonomy and loyal cooperation among European institutions and Member States. The model is then applied to gain a better understanding of the delegation problem. As is well known, a crucial normative obstacle to the delegation of regulatory powers to independent European agencies is the principle of institutional balance. By way of contrast, separation-of-powers has not prevented the US Congress from delegating extensive rule-making powers to independent commissions and agencies. Comparison with the philosophy of mixed government explains this difference. The same philosophy suggests the direction of regulatory reform. The growing complexity of EC policy making should be matched by greater functional differentiation, and in particular by the explicit acknowledgement of an autonomous ‘regulatory estate’. At a time when the Commission aspires to become the sole European executive, as in a parliamentary system, it is particularly important to stress the importance of separating the regulatory function from general executive power. The notion of a regulatory estate is meant to emphasise this need.