by John George Nicolay and John Hay, Abraham Lincoln: A History (1890)
“ Under the complex American system of government, in which the Federal Union and the several States each claim sovereignty and independent action within certain limitations, it became the theory and practice that towards each other the several States occupied the attitude of foreign nations, which relation was governed by international law, and that the principle of comity alone controlled the recognition and enforcement by any State of the law of any other State. ”
