Well... except for that little matter of Dred Scott v. Sanford...
The North did not accept it, and the only part that wasn't supported by American law is the claim that African descended people could never be citizens.
The rest of it was legally accurate and supported by the existing body of law.
And the North absolutely refused to accept it, and threw a fit about it the way Liberals today do about sanctuary cities and border security. They simply don't want to obey laws they don't like.