They weren't held in labor, or labour, because they had been freed.
But I am well familiar with the phenomena of people who see nothing wrong with ignoring aspects of constitutional law they don't like.
And I'm familiar with the similar situation of people who have only the sketchiest idea of what the Constitution said.
You always go around in a circle. The state law had not been repealed. The Constitution does not give the President the power to repeal state laws. The Constitution requires that so long as the state law exists, it must be obeyed.
Lincoln seized a power he was not granted under the constitution, and people are okay with it because they approve of the result. It's just another case of supporting an outcome rather than supporting the concept of law.
Another example of Government of men, and not of laws.