After the Civil War, most of the former slave states passed laws which became known as the "black codes" as a way to keep the African American population subservient to white people. The idea was to place restrictions on the newly found freedoms of African Americans, and to steer them back towards low wage agricultural work on farms and plantations like the ones they had been used as slaves on.

One way that this was accomplished was by passing vagrancy laws. These laws were written as vaguely as possible to avoid being unconstitutional. They typically required people to be employed, and targeted black people. The penalty for violating vagrancy laws usually was a fine, which, more often than not, the person couldn't afford to pay. When the fine was unable to be paid, the guilty party was forced to work off their debt, often times on a privately owned plantation.

Annual labor contracts were also required of African Americans in many states. They were required to show proof of employment to avoid violating vagrancy laws. In an attempt to comply with the state's laws, many African Americans took jobs working on plantations because that was the only thing they had been trained to do. The black codes put restrictions on black people's ability to own property in many cases, so often they were forced to rent land from plantation owners, and had to purchase supplies and other necessaries from the land owners along with giving them a percentage of their profits each year. This caused them to fall into debt which they weren't able to work their way out of. This in turn forced them to remain on the farm or plantation indefinitely.

These restrictive laws are examples of how African Americans were more or less forced back into slavery, even after the practice had been abolished. I hope this is what you were looking for.