Fundamentals of Business Laws and Business Communication · Sources of Law

Custom, Usage and Other Sources of Law Explained

Updated 10 October 2026 · Fact-checked

Custom is a long-followed practice that people treat as binding and courts recognise as law. Usage is a similar habit, but without the same binding force. Other sources include personal laws, international conventions, and secondary sources such as books and commission reports. In MCQs, match each term to its test.

Understand Customs, Usages and Other Sources

Law does not come only from Acts of Parliament. Some law grows out of how people actually behave over many years. This is where custom comes in.

A custom is a rule of conduct that a community has followed for a very long time and regards as binding. Courts accept it as law if it meets certain tests. It must be ancient, continuous, certain, reasonable, followed as a matter of obligation, and not against statute or public policy. A custom that clashes with an Act of the legislature will not be enforced.

A usage is a habit or practice, often in a trade or business, that is generally followed in a place or market. It does not, by itself, bind anyone. It becomes part of a contract only when the parties adopt it expressly or by implication, and only if it is not inconsistent with the contract's terms or the law. So the key difference: custom binds as law, usage binds only through the parties' agreement.

Personal laws apply to people because of their religion or community. They cover matters such as marriage, divorce, succession, adoption and maintenance. Hindu, Muslim, Christian and Parsi communities have their own rules, some written in statutes and some drawn from religious texts and custom. They apply to individuals as members of a community, not to everyone.

International conventions and treaties are agreements between countries. They do not automatically become Indian law. They take effect domestically when Parliament passes a law to give them effect. Secondary sources do not create law but help explain it. These include legal textbooks, commentaries, law commission reports and expert opinions. Courts may refer to them for guidance, but they are not binding.

Key formulas to remember

Tests of a valid custom: Ancient + Continuous + Certain + Reasonable + Obligatory + Not against statute or public policy; A custom failing any one test will not be enforced by courts as law.
Custom vs usage: Custom = binding as law; Usage = binding only if adopted by the parties; Usage is common in trade and must not contradict the contract or the law.
Personal laws: Apply by religion or community to family matters; Marriage, divorce, succession, adoption, maintenance.
International conventions: Treaty binds India internationally; domestic force needs Parliament's law; Signing alone does not change Indian law.
Secondary sources: Books, commission reports, expert opinions = persuasive, not binding; They explain or suggest law; they do not make it.

How to solve Customs, Usages and Other Sources questions

Use this method for any question on custom, usage and other sources.

1Read the question and spot the keyword: custom, usage, personal law, convention, book or commission.
2Ask if the item is binding by itself. Custom and statutes are; usage and books are not.
3If it is custom, check the tests: ancient, continuous, certain, reasonable, obligatory, not against law.
4If it is usage, look for whether the parties agreed to it, expressly or by implication.
5If it is personal law, link it to religion or community and family matters.
6If it is a convention, ask whether Parliament has legislated to give it effect.
7Eliminate options that overstate, such as 'always binding' or 'applies to everyone'.
8Pick the option that matches the exact definition.

Quickest way: Binding or not: a 10-second filter

When to use it: Use it for one-line MCQs asking which source is binding, or the difference between two terms.

Custom: think 'old, regular, felt as binding'.
Usage: think 'trade habit, needs the parties' agreement'.
Personal law: think 'religion, family matters'.
Convention: think 'needs an Indian law to apply at home'.
Books and reports: think 'persuasive only'.
Cross out options that give the wrong binding status.

Common mistakes in Customs, Usages and Other Sources

Treating custom and usage as the same thing.
Both mean a repeated practice, so they sound alike.
Fix: Remember that custom has the force of law, while usage binds only if parties adopt it.
Thinking an ancient custom overrides an Act.
Students assume age gives a custom unlimited power.
Fix: A custom must not be against statute or public policy. If it is, the Act prevails.
Saying personal laws apply to every citizen.
Students mix them up with general laws like the Indian Contract Act.
Fix: Personal laws apply by religion or community, and only to family-type matters.
Believing a signed international treaty is automatically Indian law.
Students confuse international obligation with domestic enforceability.
Fix: Remember that Parliament must make a law to give it effect within India.
Calling books and law commission reports binding sources.
They carry authority and are quoted in courts.
Fix: Label them secondary and persuasive. They guide but do not bind.

Worked examples

Example 1

Which one of the following best describes the difference between custom and usage? (A) Both are binding in the same way (B) Custom has binding force as law, while usage binds only when the parties adopt it (C) Usage is always older than custom (D) Custom applies only in trade

Show the solution

Recall: custom is a long-followed practice accepted by courts as law.
Recall: usage is a habit, often in trade, which binds only through the parties' agreement.
Option A says both bind equally. This is wrong.
Option C and D are not true: age is not the difference, and custom is not limited to trade.
Option B matches the definitions.

Answer: (B) Custom has binding force as law, while usage binds only when the parties adopt it.

Example 2

A community follows a practice for many generations, but a recent Act prohibits it. Will a court enforce the practice as a valid custom? (A) Yes, because it is ancient (B) Yes, because the community follows it (C) No, because a custom cannot be against a statute (D) No, because custom is never a source of law

Show the solution

List the tests of a valid custom, which include not being against statute or public policy.
The practice conflicts with an Act, so it fails that test.
Options A and B rely only on age and community acceptance, which are not enough.
Option D is wrong because custom is a recognised source of law when valid.
Option C states the correct reason.

Answer: (C) No, because a custom cannot be against a statute.

Exam tips

Expect direct definition questions: pick the option with the correct binding status.
When an option says 'always' or 'automatically', check it carefully. It is often a trap.
For custom, remember the full list of tests in case a question asks which is not required.
Link secondary sources with the word 'persuasive' to avoid confusing them with primary sources.
Because there is no negative marking, attempt every question even if you must guess after eliminating options.

Practice questions from Sources of Law

Customs, Usages and Other Sources in other exams

The same ground in other exams, if you are preparing for more than one or want another angle on it.

Customs, Usages and Other Sources: frequently asked questions

What is the main difference between custom and usage?

Custom is a long-established practice that courts treat as law once it meets the required tests. Usage is a habit, usually in a trade, which binds only if the parties adopt it in their contract.

What conditions must a custom satisfy to be valid?

It must be ancient, continuous, certain, reasonable and followed as obligatory. It must also not be against statute or public policy.

Are personal laws a source of law in India?

Yes. They govern matters such as marriage, divorce, succession and adoption for members of a religion or community. They apply through statutes and community rules, not to everyone alike.

Are books and law commission reports binding?

No. They are secondary sources that explain or recommend law. Courts may refer to them for guidance, but they do not create binding law.