According to the rules of war at the time, Lincoln was a war criminal and should have been hung. Booth should not have taken the law into his own hands but Lincoln, Sherman, Grant, Sheridan, were war criminals.
"This 1758 work by Swiss legal philosopher Emmerich de Vattel is of special importance to scholars of constitutional history and law, for it was read by many of the Founders of the United States of America, and informed their understanding of the principles of law which became established in the Constitution of 1787. Chitty's notes and the appended commentaries by Edward D. Ingraham, used in lectures at William and Mary College, provide a valuable perspective on Vattel's exposition from the viewpoint of American jurists who had adapted those principles to the American legal experience."
It was consider criminal by many nations to attack cities, unarmed civilians, or to destroy private property.
Henry Halleck used the above text to teach the men at West Point how to properly conduct a war. Obviously, all that went out the window when power-mad empire builders like Lincoln came along. I think he sold his soul to the railroads and bankers, to establish the precedent for empire.
He should have been hung.