Unconstitutional constitutional amendment

An unconstitutional constitutional amendment is a concept in judicial review based on the idea that even a properly passed and properly ratified constitutional amendment, specifically one that is not explicitly prohibited by a constitution's text, can nevertheless be unconstitutional on substantive (as opposed to procedural) grounds—such as due to this amendment conflicting with some constitutional or even extra-constitutional norm, value, and/or principle. As Israeli legal academic He 2017 book Unconstitutional Constitutional Amendments: The Limits of Amendment Powers demonstrates, the unconstitutional constitutional amendment doctrine has been adopted by various courts and legal scholars in various countries throughout history. While this doctrine has generally applied specifically to constitutional amendments, there have been moves and proposals to also apply this doctrine to original parts of a constitution. The idea of an unconstitutional constitutional amendment has been around since at least the 1890s—with it being embraced by former Michigan Supreme Court Chief Justice Thomas M. Cooley in 1893 and US law professor Arthur Machen in 1910 (in Machen's case, in arguing that the Fifteenth Amendment to the United States Constitution might be unconstitutional). This theory is based on the idea that there is a difference between amending a particular constitution (in other words, the constitution-amending power or the secondary constituent power) and revising it to such an extent that it is essentially a new constitution (in other words, the constitution-making power or the primary constituent power)—with proponents of this idea viewing the former as being acceptable while viewing the latter as being unacceptable (even if the existing constitution doesn't actually explicitly prohibit doing the latter through its amendment process) unless the people actually adopt a new constitution using their constitution-making power. Thomas M. Cooley insisted that amendments "cannot be revolutionary; they must be harmonious with the body of the instrument".