How did Presidential Reconstruction allow black codes to be passed?

Black codes were restrictive laws designed to limit the freedom of African Americans and ensure their availability as a cheap labor force after slavery was abolished during the Civil War. Though the Union victory had given some 4 million slaves their freedom, the question of freed blacks’ status in the postwar South was still very much unresolved.

Explanation:

a big wall across the mexican border so no drugs, terrorist, or illegal immigrants can come through : )    

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