## Facts

- The plaintiffs owned the British trading ship *Tarleton*, positioned off the West African coast to trade goods with local inhabitants.
- The *Tarleton*’s master sent a smaller trading vessel, the *Bannister*, to trade at another point on the coast.
- As local canoes approached the *Bannister* to trade, the defendant, master of a rival vessel operating nearby, ordered a cannon fired at the locals.
- The cannon shot killed one person and frightened others away, preventing trade with the plaintiffs.
- Evidence showed the defendant acted deliberately to stop locals from trading with the plaintiffs, including to compel payment of a debt the defendant claimed was owed to him.
- The defendant argued the plaintiffs had not paid a duty allegedly required by local custom before Europeans could trade, and therefore the plaintiffs’ trade was unlawful and not protected.

## Issues

1. Whether a tort action lies where a competitor intentionally uses violence or intimidation against third parties to prevent them from trading with the plaintiff, despite the absence of any formed contracts.
2. Whether the plaintiffs’ failure to comply with a local trading duty bars recovery on the ground that the frustrated trade was unlawful.

## Decision

- Judgment was entered for the plaintiffs.
- The court held that intentionally firing on third parties to frighten them away and thereby prevent trade with the plaintiffs is actionable interference with the plaintiffs’ trade.
- The court rejected the illegality defense, reasoning that enforcement of any local duty was for the local sovereign, not a private rival; the defendant had no right to enforce such norms through self-help violence.

## Legal Principles

- A defendant is liable in tort when, without lawful authority, the defendant intentionally and maliciously interferes with another’s trade or expected trade by independently unlawful means, including threats or violence directed at third parties.
- An existing contract with the deterred third parties is not required when the plaintiff had a concrete expectancy of imminent trade and the defendant wrongfully prevented it by unlawful means.
- A defendant cannot justify intentional, violent interference by pointing to the plaintiff’s alleged noncompliance with local trading requirements where the defendant lacks authority to enforce those requirements and instead takes the law into private hands.

## Conclusion

The court recognized liability for intentional interference with prospective trade where the defendant used violence to deter potential customers, and it refused to allow a private competitor to invoke alleged illegality as a pretext for self-help enforcement through intimidation.


Tarleton v. M’Gawley, 170 Eng. Rep. 153 (K.B. 1793)