The best answer? Justice Nelson’s concurrence in Dred Scott v. Sandford

The merits, comparative and absolute, of Justice Samuel Nelson’s concurring opinion in the Dred Scott case of 1857 have not been adequately recognized. Nelson took ground that was legally more secure at the time than did either Chief Justice Taney, in his opinion for the Court, or the dissenters, Justices McLean and Curtis. Refusing to follow Taney’s ill-supported denials of Black citizenship and Congressional power over the Territories, he also understood better than the dissenters what conflict-of-laws doctrine, the precedent of Swift v. Tyson (1842), and the law of marriage and divorce implied for Scott. Nelson’s opinion carried a mix of political implications, but it possessed more credibility than the other opinions in the case for its solid grounding in accepted legal principles and freedom from overt partisanship.