James McCune Smith enjoyed exposing Americans’ ignorance of classical languages and traditions. In 1859 he criticized the Supreme Court for misunderstanding the meaning of “citizenship” in the Roman Republic. Such ignorance had led the Court, in Dred Scott v. Sandford (1857), to conclude erroneously that neither slaves nor their descendants could be citizens; as Chief Justice Roger Taney wrote in his majority opinion, blacks “had no rights which the white man was bound to respect.” In his supporting opinion, Justice Peter Daniel, a proslavery Virginian, quoted extensively from the Justinian code of Roman law, which had become an important source of American law concerning slavery. He too, made numerous errors in translation and interpretation, according to McCune Smith. Similarly, Theodore Woolsey, President of Yale College and arguably the nation's preeminent Greek scholar, also reviewed the classical quotations in Daniel's opinion and highlighted the justice's many “blunders” and “absurd” translations. McCune Smith praised Woolsey's review, but he also noted that on one point the professor was “hardly clear” and thus obfuscated the Roman law of slavery; so he corrected him:

McCune Smith's larger point was that free blacks’ right to citizenship in the U.S., regardless whether they were born free or slave, was based upon the “firm foundation” of Roman law. This was because Roman law granted citizenship both to engenui and libertini, and since the U.S. Constitution lacked “any definition of the word” citizenship, “the word must bear the meaning which language itself attaches to it under like circumstances, to wit, when it expresses the relation of the individual to the general government, as in Roman polity.” For McCune Smith, Roman law provided the precedent for blacks’ right to citizenship in the U.S. “In order to impeach that right it will be necessary to blot out from history the annals of lofty Rome, to erase from language the word citizen, and to erase from human polity the relation which the individual bears to the State in a republic.”