Concept:
- India is a federal country, so the Constitution has to state clearly which government may make law on which subject.
- It does this by dividing subjects into three lists, and by fixing who takes charge of anything left over.
Step 1: The Union List.
This contains subjects of
national importance, such as
defence of the country, foreign affairs, banking, communications and currency.
They are placed here because the whole country needs one uniform policy on them, and only the
Union Government can make laws on these subjects.
Step 2: The State List.
This contains subjects of
state and local importance, such as
police, trade, commerce, agriculture and irrigation.
Only the
State Governments can make laws on these, since conditions differ greatly from one state to another.
Step 3: The Concurrent List.
This contains subjects of common interest to both, such as
education, forest, trade unions, marriage, adoption and succession.
Both the Union and the State Governments can make laws on these subjects. If their laws conflict, the
law made by the Union Government prevails.
Step 4: Subjects that fall in none of the lists.
New subjects appear that the makers of the Constitution could not have foreseen,
computer software being one example. These are called
residuary subjects, and the power to legislate on them rests with the
Union Government.
Step 5: Why the division cannot be changed easily.
This three fold distribution cannot be altered by one government acting alone. Any change needs to be passed by both Houses of Parliament with at least two thirds of the members present and voting, and then ratified by the legislatures of at least half the states.
Final Answer: The Constitution divides subjects into a Union List for the centre, a State List for the states, and a Concurrent List on which both may legislate with the union law prevailing in case of conflict, while residuary subjects such as computer software rest with the Union Government.