One of the most important features of a constitutional democracy - which is what South Africa has been since 1994 - is constitutional supremacy.

South Africa did in fact have a constitution before the interim Constitution of 1994 and the final Constitution of 1996 (see history of the Constitution). But that "tricameral" constitution - which created separate parliaments for whites, coloureds and Indians but denied blacks a say in government - was not supreme. It was subject to the whims of parliament - in this case, an unrepresentative one.

Parliamentary sovereignty meant that members of parliament could pass any laws they liked - as long as the correct procedure was followed, it didn't matter if the constitution was violated. Back then the courts had no power to scrutinise and overrule any legislation that violated human rights; nor had any such rights been entrenched in that constitution.

But all this changed in 1994, when South Africa became a constitutional democracy and what was then the interim Constitution became the highest source of authority in the land. Now, of course, the final Constitution is superior to parliament and is the yardstick by which all other laws are judged. It applies to all organs of government - including parliament, the presidency, the police force, the army and the public service.

The supreme status of the Constitution is set out early in the text. Section 2 of Chapter 1 - which deals with founding provisions - is a crucial one. It is entitled "Supremacy of Constitution" and says: "This Constitution is the supreme law of the Republic; law or conduct inconsistent with it is invalid, and the obligations imposed by it must be fulfilled."

This means any law that violates the Constitution, or any conduct that conflicts with it, can be challenged and struck down by the courts.

And this is possible because, in a constitutional democracy where power is properly shared by the executive, the legislature and the judiciary, the courts are independent and subject only to the law and the Constitution itself.

This brings us to the doctrine of the separation of powers.