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 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.
Concept
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". Elaborating on this point, Cooley argued that "an amendment converting a democratic republican government into an aristocracy or a monarchy would not be an amendment, but rather a revolution" that would require the creation and adoption of a new constitution even if the text of the existing constitution didn't actually prohibit such an amendment.
In a 1991 law review article, United States law professor Richard George Wright argues that if a constitutional amendment leaves a constitution in such a state that it is a "smoldering, meaningless wreckage" and extremely internally inconsistent and incoherent, then such an amendment should indeed be declared unconstitutional. Wright compares this to a scenario of a body rejecting a tissue transplant due to this transplant being extremely incompatible with the body to which it is grafted—thus triggering an immune response on the part of the body. In Wright's analogy, the constitution is the body and the amendment is a tissue transplant and while both can peacefully coexist separately, they cannot peacefully coexist together. While Wright rejects the idea that certain specific hypothetical amendments are unconstitutional (such as an amendment that abolishes one or more US states), Wright does agree with Yale law professor Akhil Amar's view that a hypothetical constitutional amendment that completely abolishes freedom of speech would be unconstitutional because such an amendment would also undermine many other US constitutional provisions and thus "leave standing only a disjointed, unworkably insufficient, fragmentary constitutional structure." Such an amendment would not only conflict with the provisions of the US Constitution's First Amendment—such an override being in fact not unheard of—but also with an innumerable multitude of other US constitutional provisions. Wright also agrees with US law professor Walter F. Murphy's view that a constitutional amendment that legally enshrines white supremacy, limits the franchise to whites, requires both US state governments and the US federal governments to segregate public institutions, and authorizes other legal disabilities that clearly offend and even deny the human dignity of non-whites would be unconstitutional because–in spite of such an amendment's compatibility with the pre-Civil War US Constitution–such an amendment "conflicts fundamentally and irreconcilably with virtually all conceptions of the commonly cited constitutional value of equality."