In Douglass & Mandeville v. McAllister, the Supreme Court of the United States heard a case involving an alleged breach of contract between two parties. The plaintiffs, Douglass and Mandeville, had entered into a contract with defendant McAllister to transport goods from New York to Philadelphia for them in exchange for payment. When they failed to pay him as agreed upon, he refused to deliver their goods and instead sold them at auction in order to recoup his losses. The plaintiffs argued that this was a violation of their contractual agreement and sought damages from McAllister as compensation for his actions. In its decision, the court held that while it could not award damages due to lack of evidence presented by either party regarding any actual harm suffered by either side due to the breach of contract, it did find that there had been an unjust enrichment on behalf of McAllister since he received money from selling off the plaintiff's property without permission or legal authority. As such, they ordered him return those funds back plus interest accrued during this time period so as not be unjustly enriched further at their expense

In Douglass & Mandeville v. McAllister, Justice William Johnson wrote a dissenting opinion in which he argued that the majority had incorrectly interpreted the law and failed to consider all relevant facts of the case. He noted that while it was true that there were no specific laws governing this particular situation, general principles of equity should be applied to ensure justice for both parties. Furthermore, he argued that if one party was allowed to benefit from their own wrong-doing then it would set an unfair precedent and lead to further injustice down the line. In conclusion, Justice Johnson believed that since neither party had acted with malice or fraud they should each receive equitable relief according to what is just and right under common law principles.