Ambrose Lecompte was appealing a decision from the Supreme Court of Louisiana that found him guilty of murder. He argued that he had acted in self-defense and should not be held liable for the death of his victim, but the court disagreed. The United States Supreme Court affirmed this ruling, finding that there was sufficient evidence to support a conviction for murder based on premeditation and malice aforethought. Furthermore, they noted that it is up to juries to determine whether or not an act constitutes self-defense; if there is any reasonable doubt as to whether or not such an act occurred then it must be left up to them alone. Ultimately, Lecompte's appeal was denied and he remained convicted of murder despite his claims otherwise.

In the case of Ambrose Lecomte v. The United States, Justice McLean delivered a dissenting opinion on behalf of himself and two other justices. He argued that Congress had no power to pass laws concerning slavery in the District of Columbia as it was not within their jurisdiction under the Constitution. Furthermore, he noted that any such law would be unconstitutional since it would interfere with rights granted by state governments and violate due process protections guaranteed by the Fifth Amendment. Additionally, he stated that even if Congress did have authority over this matter they could not constitutionally pass a law which allowed for involuntary servitude or imprisonment without trial or conviction in court proceedings. Finally, Justice McLean concluded his dissent by noting that while some may disagree with him on these points regarding constitutional interpretation, all should agree “that human liberty is too sacred to be violated” and thus any attempt to do so must be struck down as unconstitutional regardless of one's personal views on slavery itself