Can an enslaved person commit treason? The case of Billy

In November 1775, Virginia's royal governor, the earl of Dunmore, declared martial law and offered freedom to enslaved people who fought for the king against their owners. The Declaration of Independence referred to that proclamation in charging that the king and his governor "excited domestic Insurrections amongst us." The Declaration's statement that all men were entitled to "life, liberty, and the pursuit of happiness" did not apply to enslaved Virginians.

The summary of Billy's trial included the accusation that he "did in Company of & Conjunction with diverse Enemies of the Commonwealth in armed Vessels feloniously & Traiterously Wage & Levy War against the Commonwealth." His lawyers argued that he was "forced on board agst. his will" and that as a slave he was not afforded the privileges of a citizen, so he owed the state "no Allegiance."

Page also included an opinion from Henry Lee and William Carr, justices who dissented from the verdict and supported Page's efforts to commute the death sentence.
Independence made white Americans citizens of a new nation, but enslaved people did not enjoy most of the rights of citizenship. Did that mean that they could not commit treason? In 1781 the Prince William County Court tried an enslaved man named Billy for treason for attempting to escape to the British and supplying them with "aid and comfort."
Billy was tried and convicted in Prince William County on May 8, 1781. The court sentenced him to death by hanging and ordered that his head be mounted on a pole at the intersection of public roads.
Three of the justices of the peace appealed to governor Thomas Jefferson to issue a reprieve. They argued that slaves were not citizens and therefore could not commit treason. The executor of the estate of Billy's owner also petitioned the Virginia House of Delegates for Billy's pardon. On June 14, 1781, the General Assembly pardoned Billy because he was not a citizen.
What is treason?
The 1776 Virginia law defined treason as going to war against the Commonwealth of Virginia or providing its enemies with "aid and comfort" or other support. Conviction required either a confession in court or testimony by two eyewitnesses.
Why didn't Thomas Jefferson pardon Billy?
The Virginia treason act of 1776 granted the power to issue pardons in cases of treason to the General Assembly, not to the governor.
That was the law. Was it justice?