This article brings classic constitutionalism to an analysis of delegated legislation in the European Union. To facilitate such a constitutional analysis, it starts with a comparative excursion introducing the judicial and political safeguards on executive legislation in American constitutionalism. In the European legal order, similar constitutional safeguards emerged in the last fifty years. First, the Court of Justice developed judicial safeguards in the form of a European non-delegation doctrine. Second, the European legislator has also insisted on political safeguards within delegated legislation. Under the Rome Treaty, ‘comitology’ was the defining characteristic of executive legislation. The Lisbon Treaty represents a revolutionary restructuring of the regulatory process. The (old) Community regime for delegated legislation is split into two halves. Article 290 of the Treaty on the Functioning of the European Union (TFEU) henceforth governs delegations of legislative power, while Article 291 TFEU establishes the constitutional regime for delegations of executive power.