The doctrine of parliamentary sovereignty of the United Kingdom parliament is often presented as a unique legal arrangement, one without parallel in comparative constitutional law. By giving unconditional power to the Westminster parliament, it appears to rule out any comparison between the Westminster Parliament and the United States Congress or the German Bundestag, whose powers are limited by their respective constitutions. Parliament in the UK appears to determine the law unconditionally and without limit. Nevertheless, a fuller understanding of parliamentary sovereignty as a legal and constitutional doctrine shows that this first impression is false. The nature of the British unwritten constitutional order is entirely similar to the written one prevailing in the United States or Germany. This is because the doctrine of parliamentary sovereignty, contrary to Dicey’s classic view, does not consist in a single dominant idea but in a number of related and mutually supporting principles that constitute higher law. The way in which these principles interact is parallel to the interaction of the main clauses of the United States Constitution or the German Basic Law. This analysis shows that the constitution, written or unwritten, never requires a pouvoir constituent. The constitution emerges from the law as the result of moral and political principles that breathe life into our public institutions.