The First Confiscation Act of 1861 authorized the confiscation of any Confederate property by Union forces ("property" included slaves). This meant that all slaves that fought or worked for the Confederate military were freed whenever they were "confiscated" by Union troops. The bill passed in the House 60-48 and in the Senate 24-11. The act was signed into law by President Lincoln on August 6, 1861.
The Second Confiscation Act was passed on July 17, 1862. It stated that the slaves of any Confederate official, military or civilian, who did not surrender within 60 days of the act's passage would be freed. However, this act was only applicable to Confederate areas that had already been occupied by the Union Army. All slaves that took refuge in Union areas were "captives of war" and would be set free.
U.S. President Abraham Lincoln opposed these acts, believing that they would push the border states towards siding with the Confederacy. The growing movement towards emancipation was aided by these acts, which eventually led to the Emancipation Proclamation in 1863.