I guess you missed my previous comment on the Priggs case.
And you missed mine with the link to 1835. This is where an appeals court affirms a Supreme Courts decision and affirms the same decision by state and city courts of New York.
No one got to 'decide' if someone is a legal slave. It's based on prima facia evidence....just like any other case.
From the link
It was nevertheless decided, upon solemn argument, that the law of the United States was constitutional; that the slave was not entitled to trial by jury, or by any other mode different from that prescribed by the law of congress; and he was accordingly taken back to Virginia. This was the unanimous opinion of the court. Mr. Justice Thatcher dissented, but not on the ground of the unconstitutionality of the law of congress. The same decision has been made in Pennsylvania, and also by Judge Thompson in a late case in the circuit court of the United States. In addition, if I may be permitted to refer to the decisions of the tribunals of this state, the distinguished and learned individuals who preside over the supreme court of this state and the superior court of the city of New-York, upon mature deliberation, arrived at the same conclusion.
I cannot therefore consent to overturn a doctrine which is founded upon principle, and is sustained by authority; and am accordingly of opinion that the judgment of the supreme court ought to be affirmed.
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Making special rules is exactly what was unconstitutional about Priggs. There is NO power there for it to be legislated by the States
Priggs determination also had the added liberal benefit of letting the Supreme Court say Congress could regulate that which was already regular.... basically opening the door to redetermine already settled law.
WHY is that so hard for you to understand?