As President, Abraham Lincoln had the power to issue the Emancipation Proclamation. But it was an executive order, not a legislative mandate. The President declared the slaves free, but he had no power to regulate how former "masters" would treat former "possessions."

Presidents execute laws - they don't make them. And, significantly, Lincoln's Proclamation freed slaves in the Confederate states. What force of law would the Proclamation have in states that were no longer part of the United States? Not much, if you were a slave-owner living in a Confederate state. Not much, if your President was Jefferson Davis.

Lincoln said former slaves could fight in the Civil War, and be fully paid for it, but who would make sure they were safe once they returned home from battle? And, since Congress never passed any laws to create a process by which former slaves would become fully-participating citizens, there was room - lots of room - for future mischief.