Final answer:
Dred Scott v. Sandford ruled that slaves are not citizens and could not sue for freedom.
Step-by-step explanation:
The case that ruled that slaves are not citizens and therefore could not sue for freedom was Dred Scott v. Sandford. In this landmark Supreme Court case in 1857, the Court held that African Americans, whether enslaved or free, were not considered citizens of the United States and therefore did not have the right to bring a lawsuit. This decision further reinforced and solidified the institution of slavery in the United States prior to the Civil War.
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