In the decision, Taney makes mention that Emerson did not free Scott of his own action. The problem would be that under the Fugitive Slave Clause
[QUOTE=Article IV, Section 3, Clause 3]
No person held to service or labour in one state, under the laws thereof, escaping into another, shall, in consequence of any law or regulation therein, be discharged from such service or labour, but shall be delivered up on claim of the party to whom such service or labour may be due.
[/QUOTE]
and that there would be a difference between Emerson living in Missouri and Scott escaping to Illinois and Emerson living in Illinois and Scott “escaping” to Illinois. Without relying on the Fifth Amendment, the question Taney would face is how do you prevent the state from declaring a slave freed because otherwise you have a situation that a citizen of the sovereign State of Illinois was in effect kidnapped by Emerson and enslaved in Missouri. Looking at the opinion, Taney completely ignores the implication of
So apparently Scott was a slave in Illinois because Emerson treated him as such and Scott accepted it. Either way, Taney is stating that moving to a free state did not in of itself free Scott. Whether that made his enslavement illegal while in Illinois would still be an open question. If I live with my common law wife in Colorado where it is legal, then are we still common-law married in California where such marriages do not exist? In 2012 I believe it would be no but in 1857 what would the courts have said?
WAG but we’ve already saw how Taney made up the legal fiction that neither enslaved or free blacks could be US citizen to dispose of the issue of Scott’s standing in Federal Court. I assume Taney would create some sort of Constitutional penumbra based on the FSC and “natural order” that would state a slave cannot be freed by state action but only by given freedom by his master. If that were true, then the answer to the OP would be that slavery was legal in Cleveland but since Scott did not sue in Illinois and Taney avoided the issue by the bizarre common-law slavery idea then I believe that the legal theory that a law is valid unless shown it is unconstitutional would apply and so I stick by my statement that it was always illegal in Cleveland.