This is horribly written so I will make it simple.
It was a black American, a former slave himself, who won the right to introduce chattel slavery in the US.
Irony of history that is not well known.
Indentured servant had to be allowed to go free after 7 years. Parker went free and was going to become a servant of another man. That was Parkers choice. Johnson didnt like it and went to court to say he should be allowed to keep him. Johnson won.