Which statement best describes the fallacy in this passage?

Justice Taney assumes that the writers of the Constitution would agree with him about citizenship.
Justice Taney uses the argument that African Americans are not citizens to prove that they are not citizens.
Justice Taney assumes that the other justices on the court would agree with him about citizenship.
Justice Taney uses the argument that Dred Scott is an enslaved person to prove that he is not a citizen.