Of course the fugitive slave law required the federal government to return slaves if they were fugitives from ‘service’.
Nothing in the federal consititution required states to return slaves who were not fugitives. Judge Taney got around that by denying Dred Scott standing.
Of course if SC had a problem with the acts of NY, they had an obligation under Article III of the constitution to resolve the controversy by application to the supreme court, not by starting an insurrection or war.
Good point.