Common law refers to:

A law that is developed through decisions of a court.

Explanation:

Common law is defined as a body of legal rules that have been made by judges as they issue rulings on cases, as opposed to rules and laws made by the legislature or in official statutes. An example of common law is a rule that a judge made that says that people have a duty to read contracts and understand Situations.

the Emancipation Proclamation,

Explanation:

In 1864, President Abraham Lincoln created a legislation that prohibited slavery in United States. This legislation automatically outlawed the Maryland Assembly since it's coming from the federal level.

As a result, African Americans were free from their obligation to serve their owners. That being said, they still received very bad treatments even after gaining the status as free folks. They're treated as second class citizens, not allowed to get jobs, not allowed to vote, etc.