Holman v Johnson (1775) 1 Cowp 341 is an English contract law case concerning the principles behind illegal transactions.

It is not for his sake, however, that the objection is ever allowed; but it is founded in general principles of policy, which the defendant has the advantage of, contrary to the real justice, as between him and the plaintiff, by accident, if I may say so.

No court will lend its aid to a man who founds his cause of action upon an immoral or an illegal act.

If, from the plaintiff's own standing or otherwise, the cause of action appears to arise ex turpi causa, or the transgression of a positive law of this country, there the court says he has no right to be assisted.

Is there any law of England transgressed by a person making a complete sale of a parcel of goods at Dunkirk, and giving credit for them?

If contraband clothes are bought in France, and brought home hither; or if glass bought abroad, which ought to pay a great duty, is run into England; shall the French taylor or the glass-manufacturer stand to the risk or loss attending their being run into England?

The doctrine Huberus lays down, is founded in good sense, and upon general principles of justice.

Verum, si merx eadem alibi sit vendita, ubi non erat interdicta, emptor condemnabitur, quia, contractus inde ab initio validus fuit.” Translated, it might be rendered thus: In England, tea, which has not paid duty, is prohibited; and if sold there the contract is null and void.

But if sold and delivered at a place where it is not prohibited, as at Dunkirk, and an action is brought for the price of it in England, the buyer shall be condemned to pay the price; because the original contract was good and valid.—He goes on thus: “Verum si merces venditæ in altero loco, ubi prohibitæ sunt essent tradendæ, jam non fieret condemnatio, quia repugnaret hoc juri et commodo reipublicæ quæ merces prohibuit.” Apply this in the same manner.—But if the goods sold were to be delivered in England, where they are prohibited; the contract [345] is void, and the buyer shall not be liable in an action for the price, because it would be an inconvenience and prejudice to the State if such an action could be maintained.