I suspect you would have gotten different results from different Federal Judges. Those in the South would likely have abrogated such state laws, while those in the North likely would not have done so.
But we must contemplate what an objective judge would have done, had such a case come before him, and I don't see how someone objectively applying the laws of the day could have ignored that provision in article IV.
That would be contrary to the spirit of the times, which George Washington both understood and obeyed.
It also argues states were a lot more autonomous than they are now.
It's odd, but this is a case where you seem to be championing states rights against the Federal Constitution. I expect that soon you are going to argue that the North had a right to secede from the South over slavery. :)
The Federalist Papers and other documents show that our Founders intended Judicial Review of laws, but the Supreme Court did not start off willy-nilly striking down laws as unconstitutional.
Instead, the first example of SCOTUS declaring any law "unconstitutional" is Marbury vs. Madison in 1803 -- but that was Federal law.
The first example I can find of SCOTUS declaring a state law unconstitutional is 1824, Gibbons vs. Ogden where SCOTUS struck down a New York state law, in a commerce regulation case.
Point is: there is no possibility that the US Supreme Court in 1790 was going to strike down a Northern state's anti-slavery laws, because that was simply not part of the Founders' Original Intent & understandings.
DiogenesLamp: "But we must contemplate what an objective judge would have done, had such a case come before him, and I don't see how someone objectively applying the laws of the day could have ignored that provision in article IV."
But by "objective" you, of course, mean "whatever thoughts flitter across DiogenesLamp's brain", and that just cannot be the standard, ever.
The real standard, the only possible standard, is Founders' Original Intent, and we can see this in both what they wrote, and what they did.
In the case of slavery, it is absolutely beyond reasonable dispute that our Founders intended both that Northern states could lawfully abolish slavery, and that the Federal government could pass restrictions against it in, for examples, international waters and US western territories.
So, to declare, as in effect Roger Tanney did in Dred-Scott, that slavery must be allowed in every state, and no African-American could be a US citizen was in no way understood by our Founders, and was strongly objected to by Northern voters in 1860.
DiogenesLamp: "It also argues states were a lot more autonomous than they are now.
It's odd, but this is a case where you seem to be championing states rights against the Federal Constitution.
I expect that soon you are going to argue that the North had a right to secede from the South over slavery. :)"
Don't be ridiculous.
My argument is, and has always been, "Founders' Original Intent".
Their words and actions clearly tell us that Founders intended: slavery could be outlawed at will by Northern (or Southern) states, and restricted by Federal government outside states.
To suggest otherwise is neither historical, logical nor "objective".