When Anthony Johnson was released from his servitude, he was legally recognized as a "free Negro." He became a successful farmer. In 1651, he owned 250 acres (100 ha) and the services of five indentured servants (four white and one black). In 1653, John Casor, a black indentured servant whose contract Johnson appeared to have bought in the early 1640s, approached Captain Goldsmith, claiming his indenture had expired seven years earlier and that he was being held illegally by Johnson. A neighbor, Robert Parker, intervened and persuaded Johnson to free Casor.

Parker offered Casor work, and he signed a term of indenture to the planter. Johnson filed a Freedom suit against Parker in the Northampton Court in 1654 for the return of Casor. The court initially found in favor of Parker, but Johnson appealed. In 1655, the court reversed its ruling. Finding that Anthony Johnson still "owned" John Casor, the court ordered that he be returned with the court dues paid by Robert Parker.

This was the first instance of a judicial determination in the Thirteen Colonies holding that a person who had committed no crime could be held in servitude for life.

...Casor "was the first person who was declared an enslaved person in a civil case..." [In America.]

http://https://en.wikipedia.org/wiki/Anthony_Johnson_(colonist)

So Anthony Johnson, a free black man (who owned 4 white indentured servants) had access to the civil court system and used that access to obtain permanent ownership of a black man (Casor) - thus becoming the first person in America to do so.

How oppressed was the black "African American" Anthony Johnson?

So oppressed that, at the very least, he owned 250 acres of land, 4 white indentured servants, one black slave and could and did use the court system to successfully sue a white man.

Oh the horror!