Why could Lincoln only free the slaves in the states that were in rebellion and not all of the slaves throughout the country?

Answer

The Emancipation Proclamation only applied to states that were in rebellion against the United States. As a result, slaves in the border states that remained loyal to the Union were not affected by the Proclamation.

Q: What is the Emancipation Proclamation? A: The Emancipation Proclamation was a presidential proclamation issued by President Abraham Lincoln on January 1, 1863.
Q: What did the Emancipation Proclamation do? A: The Emancipation Proclamation declared that all slaves in the Confederate states "shall be then, thenceforward, and forever free."
Q: Why didn't the Emancipation Proclamation free all slaves? A: The Emancipation Proclamation only applied to states that were in rebellion against the United States. As a result, slaves in the border states that remained loyal to the Union were not affected by the Proclamation.