Well, Abraham Lincoln might not have said it, but he sure did ignore the US Supreme Court when in their decision they said what he was doing was UNCONSTITUTIONAL ... :-) ...
Just as secession and the first shots by the democrat rebel scum was UNCONSTITUTIONAL.
How, in any rational way could any actions taken against the confederacy and the confederate states be unconstititutional? Those states abandoned that Constitution and declared that it no longer applied to them. To claim that it was unconstitutional would mean that the Constitution does not apply to them any longer but if you do something they don’t like then it does apply to them. The democrat party still uses that false argument today.