Final answer:
The Emancipation Proclamation freed slaves in areas of rebellion against the United States, but it did not immediately free all slaves in all areas. It was a military measure based on the power to confiscate the property of traitors.
Step-by-step explanation:
The Emancipation Proclamation freed slaves in the areas that were in open rebellion against the United States. It did not immediately free slaves in the Confederate states or in the border states that were not in rebellion. The proclamation was a military measure based on the congressional power to confiscate the property of traitors.