To say that a constitution is unwritten does not meant the constitution is not writing as the name tends to imply. An unwritten constitution is one, which is partly written and partly unwritten. The parts that are unwritten are called conventions or customs. In other words, an unwritten constitution consist of customs and conventions which are reinforced by judicial precedents.
The British Constitution, for example, is said to be unwritten largely because many of the written laws are not codified; second, many of the laws are not writable (they cannot be written), and finally, the British people have not sat down to deliberately write a constitution. The which is practice has been the result of customs, practices, precepts and other usages which have developed with time.
New Zealand and Israel are also countries which have unwritten constitution. In the case of Israel,H.E. Baker points out that there are basic laws, but there is no constitution drawn up.
The unwritten constitution has the following disadvantages.
Because an unwritten constitution is not definite, an ambitious leader may abandon it and rule according to his own whims and caprices thereby encouraging dictatorship and abuse of power. For example, President Franklin Roosevelt ran for a third term in 1944 and the unwritten rule that an American President should not run for a third term was ignored. This invariably resorted in the amendment of the USA constitution to limit the power of the president to a maximum of two terms of four years.
It is not suitable for a large heterogeneous state like Nigeria, which has different peoples, cultures, languages and religions.
An unwritten constitution does not adequately protect minority interests.
Since there are so many laws, customs, conventions and precedents, it may be difficult for the citizens to know their rights and duties.