An entrenched clause whose intent is to prevent subsequent amendments, will, once it is adopted, and provided that it is correctly drafted, make some portion of a constitution irrevocable except through the assertion of the right of revolution.
Any amendment to a constitution which would not satisfy the prerequisites enshrined in a valid entreched clause would lead to so-called "unconstitutional constitutional law", i.e. an amendment to constitutional law text which would appear to be constitutional law only by its form, albeit being unconstitutional as with respect to the procedure in which it has been enacted, or as to the material content of its provisions.
Entrenched clauses are, in some cases, justified as protecting the rights of a minority from the dangers of majoritarianism, but they are often challenged by their opponents as being particularly undemocratic. In other cases, the objective may be to prevent amendments to the constitution which would pervert the fundamental principles enshrined in it, in particular to prevent the creation of a "legalistic" dictatorship.
As examples of inadmissible constitutional amendments, Article Five of the United States Constitution contained two entrenched clauses. One clause prohibited any constitutional amendment regarding the international slave trade. This clause expired in 1808. The other clause, still in effect, states that "no State, without its Consent, shall be deprived of its equal suffrage in the Senate". This has been interpreted to require unanimous ratification of any amendment altering the composition of the United States Senate. However, the text of the clause would indicate that the size of the Senate could be changed by an ordinary amendment if each state continued to have equal representation. The unratified Corwin Amendment would have amounted to another entrenched clause, protecting states' rights to continue slavery.
The Basic Law for the Federal Republic of Germany, which forms the federal constitution of Germany, provides in its Article 79 section 3, that any constitutional amendment would be inadmissible, if such amendment would provide that Germany would not consist of states (Länder) any more, that the Länder would not be entitled any more to participate in the federal law-making procedures, or if the following constitutional principles would be affected: The inviolability of the dignity of man and the respect to and protection of it by any official power, the fundamental validity of human rights, the commitment of the state to basic rights, the name of the state, this including its denomination as republic, democracy, the principle of being a social state, sovereignty of the people, which is exercised by elections and referendums, separation of powers of the legislative, the executive, and the judiciary, the requirement of the constitutionality of legislation, the submission of the executive and the judiciary to the complete legal order, and finally the legal right of all citizens to resist any person who tries to overthrow this order, if other remedy is not available ("right to resistance"). The original purpose of this eternity clause was to ensure that the establishment of any dictatorship in Germany would be clearly illegal; in legal practice, the clause was used by plaintiffs at the Federal Consitutional Court challenging constitutional amendments which allowed Germany to form part of the European Union, unsuccessfully claiming that those amendments would affect the eternal principle of sovereignty of the people.
Another example of entrenchment would be the entrenching of portions of the Malaysian Constitution related to the Malaysian social contract, which specifies that citizenship be granted to the substantial Chinese and Indian immigrant populations in return for the recognition of a special position for the indigenous Malay majority. The Constitution did not initially contain an entrenched clause; indeed, one of the articles later entrenched, Article 153, was initially intended to be subject to a sunset clause. However, after the May 13 incident of racial rioting in 1969, Parliament passed the Constitution (Amendment) Act 1971. The Act permitted criminalisation of the questioning of Articles 152, 153, 181, and Part III of the Constitution. Article 152 specifies the Malay language as the national language of Malaysia; Article 153 grants the Malays special privileges; Article 181 covers the position of the Malay rulers; and Part III deals with matters of citizenship. The restrictions, which even covered Members of Parliament, made the repeal of these sections of the Constitution unamendable or repealable by de facto; however, to further entrench them, the Act also amended Article 159(5), which covers Constitutional amendments, to prohibit the amending of the aforementioned Articles, as well as Article 159(5), without the consent of the Conference of Rulers — a non-elected body comprising the rulers of the Malay states and the governors of the other states.
There are several examples of entrenched clauses which ultimately failed in their objectives, since their protections were undermined in unintended ways. The Irish Free State Constitution was required in parts to be consistent with the 1922 Anglo-Irish Treaty, including an oath of allegiance and a representative of the Crown. The checks to protect this were removed by, for example, the Irish taking control of advice to the Governor-General, and when the Senate proved obstructive its abolition. Another example of a failed entrenched clause was in the initial constitution of the Union of South Africa. The constitution's entrenched clauses protected voting rights, including those of some Coloureds, but they lost their votes after the Government packed the Senate and Supreme Court with its sympathisers.
Provisions may also be entrenched in the constitutions of legal bodies. A example is in the memoranda and articles of companies limited by guarantee, in which the principles of common ownership may be entrenched. This practice aimed to make it difficult or in practice impossible for the company's members to dissolve the company and distribute its assets among them. This idea has more recently been extended in the UK through the invention of the community interest company (CIC) which incorporates an asset lock.