What did Quinn v. Leatham decide?

It held that a conspiracy to injure a person’s business is unlawful, even if the means are usually lawful, when the intent is to cause harm and damage results.

Are unions liable for inducing customers to stop dealing?

Yes. Unions or individuals can be liable for conspiracy where they use unlawful means like blacklisting or inducing breaches of contract.

Is malicious use of a legal right always actionable?

No. A legal right used with malice is not wrongful by itself, but becomes actionable when it causes actual damage as part of a conspiracy to injure.

Does the case ban strikes?

No. Workers may strike, but liability can arise if the methods include unlawful means that aim to injure another’s business.

Why is the case still cited?

It clarifies the tort of conspiracy, distinguishing lawful competition from coordinated harm using unlawful means.

Quinn v. Leatham (1901)

Quick Summary

A union-led boycott pushed customers to stop buying from Leatham, a butcher. The House of Lords said: if people join together to harm a business, and use unlawful means (like blacklisting or inducing breaches), it is a tort—conspiracy to injure. Lawful acts done with a pure intent to harm may also be actionable when real damage follows.

Main idea: Concerted action + intent to harm + unlawful means/actual damage = liability.
Result: Leatham won damages; the defendants’ coordinated pressure crossed the line.

Issues

Did the defendants wrongfully conspire to injure Leatham’s business?
Is a conspiracy to injure actionable even if some means used are otherwise lawful?

Rules

Conspiracy to injure is unlawful where the purpose is to harm another’s business and damage occurs.
Using unlawful means (e.g., intimidation, blacklisting, inducing breach) triggers liability.
Exercising a legal right with malice is not automatically a tort—but it may be when it causes actual loss as part of a harmful plan.

Facts (Timeline)

CASE_TITLE

Henry Leatham ran a butcher’s shop in Lisburn.
He refused to employ a member of the Belfast butchers’ union (BBA).
The BBA called a strike and pushed customers to stop dealing with Leatham.
Leatham’s business suffered heavy losses.
He sued, claiming a conspiracy using unlawful means—like inducing customers to breach or end dealings.

Timeline showing boycott and losses in Quinn v. Leatham

Arguments

Leatham (Plaintiff)

Union-led plan aimed to injure his business.
Methods included inducing customers to stop dealing—unlawful means.
Real financial loss followed → damages should be awarded.

Quinn & Others (Defendants)

They exercised rights to strike and persuade.
No unlawful means; actions were part of union activity.
No actionable conspiracy as the means were not illegal per se.

Judgment

Held

Liability: For conspiracy to injure through unlawful means and intent to harm.
Union acts: Strike rights exist, but methods like blacklisting or inducing breaches create liability.
Damages: Actual financial loss made the claim actionable; damages awarded to Leatham.

Ratio Decidendi

A combination to injure, using unlawful means or causing actual damage with a harmful purpose, is actionable in tort. Collective action is not shielded if it weaponises unlawful pressure.

Why It Matters

Sets the classic rule for the tort of conspiracy to injure.
Draws a line between fair collective action and unlawful economic pressure.
Guides modern disputes involving boycotts and coordinated campaigns.

Key Takeaways

Purpose to injure + unlawful means/actual damage = conspiracy.
Inducing customers to stop dealing can be unlawful in a conspiracy.
Strike rights do not protect blacklisting or intimidation.

Mnemonic + 3-Step Hook

Mnemonic: “P-U-D” — Purpose to harm, Unlawful means, Damage proved.

Spot: Is there a plan to hurt a business?
Check: Any unlawful means or induced breach?
Prove: Real loss? If yes → liability.

IRAC Outline

Issue

Whether a coordinated boycott that induces customers to stop dealing amounts to an actionable conspiracy to injure.

Rule

Conspiracy to injure is unlawful where unlawful means are used or actual damage is intended and caused.

Application

Union pressured customers and induced them to stop dealing; this went beyond lawful persuasion and caused loss.

Conclusion

Actionable conspiracy made out; damages awarded to Leatham.

Glossary

Conspiracy to Injure: A joint plan to harm a person’s trade or business that uses unlawful means or aims at causing damage.
Unlawful Means: Conduct like intimidation, blacklisting, or inducing breach of contract.
Inducing Breach: Persuading someone to break a contract with a third party.