Yes your are looking in the wrong place. The laws are found in legislative acts and constitutional changes. The following link is to the Mississippi Supreme Court prior to the Civil War.

By this time, in order to prevent and reduce the number of Free People of Color within the State limits, the State Legislature pass laws to remove freed slaves.

The court recognized the right of an owner to remove a slave to a free state and free them there but they could not return. Also, a slave freed by a will within the state had a short period to remove themselves or be subject to losing their freedom. The court also recognized that these laws did not prevent the right of a free person of color of owning certain property, or slaves owning certain types of property within the state. Also the court recognized that certain free people of color could, under certain circumstances remain within the State.

If you read the entire findings you can see the social order and politics of the time was conflicting with moral conscience of the people.

https://books.google.cat/books?id=tfkLAAAAYAAJ&pg=PA236&dq=mississippi+state+laws+manumission&hl=ca&sa=X&ved=0ahUKEwiH_IC-i-TOAhUU2WMKHezjBsYQ6AEIITAA#v=onepage&q=mississippi%20state%20laws%20manumission&f=false