Wilson observed that the War Between the States established the federal government as the final judge of its powers. To be more accurate, let's say that the war openly brought out the big guns, used them, and raised to the surface the exercise of federal power that was already latent or had been going on for decades in a less conspicuous or thorough-going manner. Thank you for that blog, Tom.
The rule by guns, not the Constitution, means that the powers of the federal government are limited by nothing except the resistance of those under its rule and certain remaining forms and customs that are still observed under that Constitution. And both of these mean that as time passes and as the federal government extends its powers and subverts these forms and customs, it becomes more and more of a tyranny.