The question is simply this: Can a negro, whose ancestors were imported into this country, and sold as slaves, become a member of the political community formed and brought into existence by the Constitution of the United States, and as such become entitled to all the rights, and privileges, and immunities, guaranteed by that instrument to the citizen?
The words "people of the United States" and "citizens" are synonymous terms, and mean the same thing. …They both describe the political body who ... form the sovereignty [source of power], and who they are those who hold the power and conduct the Government through their representatives - the Congress, the president, etc. The question before us is, whether the class of persons described in the plea in abatement [people of African ancestry] compose a portion of this people, and are constituent members of this sovereignty? 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 no rights or privileges but such as those who held the power and the Government might choose to grant them.
...The court thinks [Dred Scott] could not be a citizen of the State of Missouri, within the meaning of the Constitution of the United States, and, consequently, was not entitled to sue in its courts... the language used in the Declaration of Independence, show, that neither the class of persons who had been imported as slaves, nor their descendants, whether they had become free or not, were then acknowledged as a part of the people, nor intended to be included in the general words used in that memorable instrument….