Ann Brabston brought a case against Tobias Gibson in the Supreme Court of the United States. She argued that she had been wrongfully deprived of her freedom by being held as a slave, despite having been born free. The court found that Ann was indeed born free and therefore could not be lawfully enslaved. It further ruled that any contract or agreement between Ann and Gibson to purchase her services was void because it violated public policy and natural justice. This decision established an important precedent for future cases involving slavery, affirming the right of all persons to their own liberty regardless of race or status at birth.

In the case of Ann Brabston v. Tobias Gibson, Justice McLean delivered a dissenting opinion in which he argued that the court should have granted relief to the plaintiff on her claim for damages against Gibson. He noted that although there was no written contract between them, it was clear from their actions and correspondence that they had entered into an agreement whereby she would receive compensation for services rendered as his agent in purchasing land. The majority opinion held otherwise because it found insufficient evidence of such an agreement; however, Justice McLean disagreed with this conclusion and believed there were sufficient facts to support a finding of liability on behalf of Gibson. He further argued that even if there was not enough proof to establish a formal contract between them, Brabston's reliance upon Gibson's promises constituted consideration sufficient to create an implied-in-fact contract under which she could recover damages for breach thereof by him.