You are not actually allowed to free a gentile slave. However as we know, a Jewish slave is freed after 6 years of work. [That is right after the Ten Commandments in Exodus.] The prohibition to free a gentile slave is from the verse בהם לעולם תעבודו (When the Torah discusses the case when one buys gentile slave it adds "you should work with them forever" i.e. not free them. So you can see the point of the South. They realized that the slaves were not seeking freedom. They were seeking mastery--i.e. to become the masters. and that has happened.
So on one hand I can see the point of Abraham Lincoln in wanting to keep the Union together, still I do not know where he found that idea in the Constitution , not even if he had, why it would supersede states rights [the tenth Ammendment.] And besides all that, the real point comes to the fore in the verse that states on three things the land is destroyed and one of them is "עבד כי ימלוך (When a slave rules)."
And the logical conclusion is that the USA should not let slaves rule.
[Rabban Gamliel had a gentile slave Tabi who was a great Torah scholar. But even so, Rabban Gamliel did not free him. Tabi himself was strict not to eat in a Suka, because slaves and women are not obligated to eat in a suka (during Sukot]).
