There's an interesting paper in the May 2004 issue of THE YALE LAW JOURNAL, according to Lawmeme. Extract from the abstract:

"The struggle to define the role of the legislature in the modern administrative state has been central to constitutional politics in Western countries. That struggle was especially intense in Germany and France from the 1920s to the 1950s. Contrary to claims of certain interwar theorists, like Carl Schmitt, the apparent demise of the legislature was not the consequence of an "insurmountable" opposition between parliamentary democracy and the demands of executive power in an era of administrative governance.
Rather, for both Germany and France, the constitutional flaw was traceable to a basic tenet of traditional republicanism inherited from the nineteenth century. This view held that a republican parliament, as the privileged institutional expression of national sovereignty, necessarily possessed plenary authority to allocate power among the branches as it alone deemed expedient in the circumstances. In the interwar period, the German and French parliaments repeatedly relied on this notion to cede full powers to the executive, a practice that ultimately provided the legal foundation for dictatorship.
After 1945, the drafters of the West German and French postwar constitutions gleaned two lessons from the interwar experience: first, that there had to be a substantive "reserve" of governing authority that a republican parliament could not delegate; and second, that an independent body had to have power to enforce those delegation constraints against the parliament itself. Although such constraints ran contrary to older conceptions of parliamentary supremacy in a republican form of government, the drafters concluded that they were necessary to ensure the place of the parliament in a democratic system of separation of powers. "

Extremely pertinent in the light of recent battles in the UK between the House of Lords and the the government over constituional reform.