McGuire v. The Commonwealth was a case heard by the United States Supreme Court in 1865. It involved an African American man, McGuire, who had been convicted of larceny and sentenced to five years hard labor in Virginia. He appealed his conviction on the grounds that he had not received due process under state law because he was denied counsel during his trial proceedings and did not have access to witnesses or evidence for his defense. The Supreme Court ruled that McGuire's rights were violated as guaranteed by the Fourteenth Amendment of the Constitution which states "no State shall make or enforce any law which shall abridge the privileges or immunities of citizens". This ruling established precedent for all future cases involving criminal defendants' right to legal representation regardless of race, gender, religion etc., thus ensuring equal protection under US law for all individuals accused of crimes.

In McGuire v. The Commonwealth, the Supreme Court of Virginia held that a slave could not be emancipated by his master without legislative action. The dissenting opinion argued that the power to free slaves was inherent in the right of property and should not be subject to government interference or regulation. Furthermore, it asserted that slavery was contrary to natural law and morality and therefore any act which tended towards emancipation should be encouraged rather than prohibited by legislation. It further contended that since there were no laws prohibiting manumission prior to 1806, masters had an implied right under common law principles to free their slaves at will; thus making any subsequent statute on this matter unconstitutional as it would interfere with vested rights already established before its enactment. Finally, it concluded that if such statutes did exist they must necessarily violate both state constitutions as well as those of the United States due to their restriction on personal liberty and freedom from arbitrary governmental control over private matters like emancipation decisions made between individuals within a state's borders.