Well, maybe I overstated Ex Parte Merryman not being appealable. Lincoln could have appealed it to the full Supreme Court if he took the position that Taney’s legitimate Supreme Court Justice at chambers ruling represented the decision of an inferior tribunal.
Now you want it both ways. The Supreme Court is the highest court in the land. There is no legal appeal from their decision. If Taney did, in fact, issue a judicial decision for the entire court all by his lonesome then that should have been the end of it. Ex Parte Milligan, Roe v. Wade, Bush v. Gore, none of those could be appealed once the Supreme Court had ruled. Why Ex Parte Merryman?