One of Lincoln's objections was to the idea that Southern states needed to "re-join" the Union (an idea that permeated the whole bill).
Moreover, the bill compelled those states to draft new Constitutions banning slavery, which was plainly unconstitutional at the time since, in the then-absence of a Constitutional amendment on the issue (which would soon pass on its own right), Congress had no power to deal with slavery within each state [REF].