What Is a Constitution?

A constitution performs three main jobs. It creates the institutions of government, distributes power between them, and sets limits on what any of them can do.

It also usually establishes how ordinary laws are made and what happens when they conflict with the constitution itself. Where a constitution is supreme, a law that contradicts it can be struck down by a court, which makes the constitution genuinely higher law rather than a statement of intent.

Most countries have a codified constitution: a single document with special status, such as the constitution of the United States or of India. Amending it usually requires a harder procedure than passing ordinary legislation.

The United Kingdom, New Zealand and Israel are the standard exceptions. Their constitutional rules are spread across statutes, court decisions and conventions. This is not an absence of a constitution but a different form of one, and its flexibility is both its strength and the main criticism of it.

Despite huge variation, most cover a similar range of subjects:

• •The structure of the legislature, executive and judiciary
• •How elections are held and how often
• •A list of protected rights and freedoms
• •The division of power between national and regional governments
• •The procedure for amending the constitution itself

How hard a constitution is to change is a deliberate design choice with real consequences. Too easy and it provides no protection, since any temporary majority can rewrite the rules that constrain it. Too hard and the country becomes unable to fix genuine problems.

Common mechanisms include supermajorities in the legislature, approval by regional states, referendums, or some combination. Some constitutions also declare certain provisions permanently unamendable, typically those establishing democracy itself or basic human dignity.

A written constitution guarantees nothing on its own. Several countries with impressive constitutional texts have very poor records in practice, because the institutions meant to enforce those texts are weak or captured.

What makes a constitution effective is whether independent courts can enforce it, whether officials expect to be held to it, and whether the public treats it as binding. Constitutional scholars call this the difference between a constitution as law and a constitution as decoration.

Researchers who have assembled data on constitutions worldwide since the late eighteenth century found that the average national constitution lasts around nineteen years before being replaced, which is far shorter than most people assume.

The United States constitution is a striking outlier, and so is its brevity, since it is one of the shortest in the world. Length and detail turn out to correlate with replacement: highly specific constitutions tend to become unworkable as circumstances change, while more general ones can be reinterpreted rather than replaced.

A constitution needs someone to interpret it when disputes arise, and countries answer that question differently. The United States constitution does not say explicitly that courts can strike down laws. The Supreme Court claimed that power in the 1803 case Marbury v Madison, reasoning that a court applying the law must prefer the constitution when an ordinary statute conflicts with it. In the American model, any court can consider whether a law is constitutional, with the Supreme Court having the final word.

Many European countries chose a different design, with a single specialised constitutional court. Austria created one in 1920, and Germany's Federal Constitutional Court, set up after the Second World War, is one of the most influential. The United Kingdom works differently again. Because Parliament is sovereign, courts cannot strike down an act of Parliament. Under the Human Rights Act 1998 they can issue a declaration of incompatibility, which leaves the law in force but puts political pressure on Parliament and ministers to change it.

Some constitutions are drafted by a specially chosen body called a constituent assembly. India's assembly began work in 1946 and debated the text for nearly three years, with B. R. Ambedkar chairing the drafting committee. The result was adopted in November 1949 and came into force on 26 January 1950, a date still marked as Republic Day. Because the debates were recorded in detail, Indian judges and lawyers still consult them today when they want to understand what a particular article was meant to achieve.

South Africa used an unusual two-stage process at the end of apartheid. Negotiators first agreed an interim constitution in 1993, which included a set of 34 constitutional principles that the final text would have to respect. An elected assembly then drafted the permanent constitution, and the new Constitutional Court had to certify that it met those principles. In 1996 the court refused to certify the first draft, sending several provisions back for revision. A corrected version was certified later that year and took effect in 1997, showing judges checking a constitution before it existed.

The United States shows how demanding amendment rules can be. Under Article V, an amendment usually needs a two-thirds vote in both houses of Congress and then ratification by three quarters of the states, which today means 38 of 50. Only 27 amendments have succeeded, and the first ten, the Bill of Rights, were ratified together in 1791. The 27th Amendment, which delays any change to the pay of members of Congress until after the next election, was proposed in 1789 but only ratified in 1992, after a university student started a campaign to revive it.

Australia offers a different test. A change to its constitution must be passed by the federal parliament and then approved at a referendum by a double majority: a majority of voters nationally and a majority of voters in at least four of the six states. Since federation in 1901, only eight of the more than forty proposals put to voters have passed. Ireland also requires a referendum for every constitutional amendment, but its voters have approved changes far more often, including on divorce and same-sex marriage. The same principle of popular approval can produce very different rates of change.

Magna Carta is often called the first constitution, but that is misleading. It was a peace settlement forced on King John by rebel barons in 1215, dealing largely with feudal grievances such as the payments owed to the king. Pope Innocent III declared it void within weeks, and civil war followed. It survived only because it was reissued in revised forms in later years. Today just three of its clauses remain law in England and Wales, including the promise that no free man shall be imprisoned except by the lawful judgement of his peers or by the law of the land.

Its lasting importance lay in the idea that even a king is bound by law, which later lawyers and American colonists invoked against royal power. For the oldest written constitutions still in force, you have to look elsewhere. The constitution of Massachusetts, drafted largely by John Adams and adopted in 1780, is usually described as the oldest functioning written constitution in the world, and it is older than the United States constitution. The small republic of San Marino sometimes claims an even older title, because its governing statutes date from 1600, though they are a collection of laws rather than a single modern-style document.

A constitution sets out who holds power, how they get it and what limits apply, whether written in one document or spread across many sources, and its real force depends on whether independent institutions can actually enforce it.