That would come as a surprise to Jeff Davis and the Confederate soldiers who were fighting after Lincoln's death.
I once ran across a lawsuit from Mississippi, I think it was. A man was accused of fraud because he went and bought something with Confederate money as soon as he had heard that Lee had surrendered but before it was widely known--the implication was that the seller would have refused to accept the Confederate money if he had realized that Lee had already surrendered.
Appomattox was April 9th. Lincoln died April 15th.