I'll agree with Kevin that citing the Dred Scott decision is an odd way to justify anything, let alone the claim that the 2nd Amendment grants an individual right to bear arms. That's an interpretation that is, at best, debatable, and Dred Scott is not considered the high water mark of American jurisprudence.
One thing about the decision has me confused. As quoted by the Wall Street Journal, the decision states:
"Although Dred Scott is as infamous as it was erroneous in holding that African-Americans are not citizens, this passage expresses the view, albeit in passing, that the Second Amendment contains a personal right."
As the Journal points out "The Supreme Court never reversed Dred Scott." If it took Constitutional amendments to reverse the decision, can it really be said to have been "erroneous"? My question isn't meant to justify Taney's decision, which I think was immoral, not to mention bad policy. I simply question whether it is accurate to say that a decision which has never been reversed could be called "erroneous."
The law is not always moral, nor does it always constitute good policy. Slavery was immoral and bad policy, but was undoubtedly constitutional until those amendments. The question in Dred Scott was whether different states could have different rules for citizenship, and whether a descendant of slaves could be a citizen. It seems that the Constitution of the day would side with the execrable Taney decision. Article 4 of the constitution states that:
No person held to service or labor in one state, under the laws thereof, escaping into another, shall, in consequence of any laws or regulations therein, be discharged from such service or labour, but shall be delivered up on claim of the party to whom such service or labor may be due.
Congress passed a Fugitive Slave Act in 1793 which enforced that provision. In 1847, the Supreme Court held that the states did not have to expend resources to capture escaped slaves, but didn't overturn the law. The 1850 Fugitive Slave Act required federal marshals and other law enforcement agencies to capture escaped slaves, and established fines for those who did not, and for anyone who harbored an escaped slave. Clearly, Congress and the Constitution did not intend that crossing state lines would change a person's citizenship, at least for federal purposes.
The Constitution does try to make the rights of citizens fairly uniform, stating that "the citizens of one state shall be entitled to all privileges and immunities of citizens in the several states."
Taney argued that if there were not a uniform federal standard for state citizenship, that clause would make many matters incoherent. Imagine if Missouri granted all the rights of citizenship to undocumented workers. Would Kansas then have to allow illegal immigrants to vote, too? Would the immigrants' legal status change when they cross between states?
I'm wondering if Kris Kobach cites Dred Scott in arguing against in-state tuition for the children of illegal immigrants. His arguments seem basically the same as Taney's, that extending in-state tuition to non-citizens is somehow creating different sorts of citizenship in different states. If Dred Scott was "erroneous," then I can see why he would ignore it, but it seems like it works to his favor.