As I said above, slavery is enshrined in our Constitution. Lincoln knew this and knew that overturning slavery would require a constitutional amendment. But the South was using slaves as a weapon of war against the north. Thus, Lincoln used another part of the Constitution, – his WAR POWERS as Commander in Chief – to legally justify the Emancipation. So technically, the Proclamation was a tool to win the war, NOT to free the slaves. Though it was an extremely popular move and the radical wing of his party was extremely happy.

But that’s not what I wanted to add here. Not only did the Emancipation Proclamation NOT APPLY to the Northern states, nor did it even apply to Washington DC, which still had slavery at the time. But the Emancipation Proclamation also DID NOT APPLY to those southern states that were occupied by Northern troops at the time the Proclamation was enacted. That’s right, the Emancipation Proclamation did not apply to those Confederate States that were now occupied territory!

Why not? Because again, Lincoln knew that the President did not have the power to override the Constitution, and slavery was enshrined in that Constitution. And in occupied territory, he could no longer use his war powers as a legal justification for emancipation.

However, it was already the law that once a slave became free, they could (generally) not be re-enslaved. Thus, as the Union army advanced, slaves in those areas could not be re-enslaved.

Lincoln did not rest with the Emancipation Proclamation. which as I pointed out above was a tool to end the Civil War. It was not an attempt to end slavery as a primary objective. And because Lincoln knew that slavery was enshrined in the Constitution, he knew that the Emancipation would probably NOT survive the war, though I believe he argued that it would. Thus, he knew the nation needed that Constitutional Amendment. But he also knew that in 1862, the nation was still not ready for the freeing of slaves. Indeed, the Democrats often tried to portray Lincoln as caring more about slavery than about the dieing of thousands of soldiers on the battlefield. So Lincoln had to tread very carefully, while at the same time appeasing the Radical Republicans. Had he moved too quickly on Slavery, the Democrats could use this in any next election. Indeed, thru much of 1864, Lincoln was doubtful of his own re-election.

Well, by the end of 1864, it was looking like the US might indeed win the war outright, and the nation was more and more moving towards the full eradication of slavery and even to allow “Some” blacks to vote. The exceptional skill and bravery of Negro Battalions in the war helped strengthen that notion.

So, by the end of 1864, and only after his reelection, Lincoln felt the nation was ready to end slavery, so gave his imprimatur to the 13th Amendment. (Had Sherman not won Atlanta prior to the election, Lincoln probably would not have been re-elected. And had the nation gotten wind of the 13th Amendment prior to the election, AND Sherman had not taken Atlanta, Lincoln absolutely would not have been reelected. Thus, the South would have re-entered the Union with slavery intact.

But history turned out differently and the 13th Amendment was introduced and passed by Congress in January of 1864 while Lincoln was still President, and the war was still going on. Then it needed 3/4ths of the 36 states to become law. 20 states passed the Amendment before Lincoln died in April of 1865. It needed another 6 before it became law, though the only reason it needed so many was because all the Southern States were still being counted as part of the total. It’s final passage was in December of 1865.

(So I would argue that Lincoln did free the slaves with the 13th Amendment and the fact that it was still 6 states short at his death an inconsequential detail.)

I’d like to point out that the Republican party back in the 1860s and 70s was quite Socialist in it’s ideas. And it was the Democratic party back then that was very much laissez faire Capitalistic — thus very much pro the property owners of slaves. Today, it’s the Republican party that cleaves to laissez faire, while even the modern Democratic party is not any where near as socialist as the Republican party of the 1860s.