The effect of the Dred Scott decision was that Congress could not prohibit slavery.
Explanation:
The case Dred Scott v. Sandford was a judicial claim, crucial in the history of the United States, resolved by the Supreme Court of that country in 1857, in which it was decided to deprive any inhabitant of African descent, whether slaves or not, the right to citizenship; and the authority to prohibit slavery in federal territories of the country was removed from Congress. The decision was drafted by Chief Justice Roger B. Taney. The fury that caused this ruling among the abolitionists was an important factor in the explosion of the Civil War.
The primary effect of the Dred Scott decision, based only on the option in this list, was that "Congress could not prohibit slavery," but mostly it meant that blacks weren't considered citizens and thus could not sue for their freedom.
