Historians of American jurisprudence are in almost complete agreement when it comes to Dred Scott v. Sandford. It is, in the words of Prof. Junius P. Robinson, "universally condemned as the U.S. Supreme Court's worst decision."

Indeed, it is scarcely possible that Chief Justice Roger B. Taney's decision could have been more ineffective when it came to settling tensions over the question of slavery. Taney's decision became an easily-critiqued flashpoint both for people with a moral objection to slavery and also for Northerners who were concerned about the political influence of the South.

Taney began from the premise that Scott could not be a citizen of the United States because he was the descendant of slaves:

We think they are not, and that they are not included, and were not intended to be included, under the word "citizens" in the Constitution, and can therefore claim none of the rights and privileges which that instrument provides for and secures to citizens of the United States. On the contrary, they were at that time considered as a subordinate and inferior class of beings who had been subjugated by the dominant race, and, whether emancipated or not, yet remained subject to their authority, and had no rights or privileges but such as those who held the power and the Government might choose to grant them.

Taney came to the rather interesting conclusion that it was possible to be the citizen of a particular state, but not of the United States:

In discussing this question, we must not confound the rights of citizenship which a State may confer within its own limits and the rights of citizenship as a member of the Union. It does not by any means follow, because he has all the rights and privileges of a citizen of a State, that he must be a citizen of the United States.

Having established that Dred Scott was not a citizen of the United States, Taney said he lacked the standing to sue for his freedom. This was the part of Taney's decision that most outraged people with a moral objection to slavery.

Taney's opinion went on to deny the federal government the right to legislate on slavery in the territories. This outraged even those Northerners who did not have strong moral objections to slavery. They felt the decision made a mockery of the good faith they had exercised in trying to compromise with the South in order to preserve the Union. Northerners worried Taney's decision would further strengthen the slave states (the free states were already badly outnumbered in the House of Representatives and had to hold the Senate to ensure a continued voice in Congress). Some free states even worried that the Supreme Court would forbid them from prohibiting slavery.

The panic sparked by the Dred Scott decision galvanized Northerners and strengthened the new Republican Party.

The Dred Scott case was absolutely ineffective in settling the conflict over slavery.  Chief Justice Taney might have thought that he was going to set the issue to rest once and for all, but he really just inflamed it.  In his decision, he said that Congress had no right to legislate on the issue of slavery in the territories.  This meant that there could no longer be any compromises (like the Missouri Compromise) between the North and the South on the issue of slavery.  Instead, it seemed to imply that every new territory or state would have to go through the sort of violence that occurred in "Bleeding Kansas."

The Dred Scott decision also made Northerners extremely suspicious of the "slave power."  It convinced them that the slaveowners of the South had the power to influence the federal government and get their way.  Because the case did this and because it closed on the possibility of compromise, the decision made the conflict over slavery worse than it had been before.