PP has the gist of it figured out, I believe. When we rebelled in 1775, one out of four Continentals died, the highest percentage per capita rate for all of our wars. The South, from northern Florida to southern North Carolina, roiled in its own civil war for more than three years, with more than 2,000 killed by their own neighbors, either in battle or banditry or ambush.
The attack by the South on the federal government in April 1861 ended only with the death of more than 600,000 American soldiers on both sides (the second highest per capita percentage rate of all our wars) and maybe another 50,000 to 80,000 dead civilians killed not only in the Border States but states such as Texas.
Our wars since 1866 against ourselves have been waged in the political arena, because (1) people generally don't die, and (2) if one side loses, it is guaranteed another chance in at least two years. This is a great deal! We can all run around and act like idiots, and no one dies.
Yes, this will be settled by SCOTUS, just as the economic recovery was in the New Deal. Parts of the far-reaching AAA and NRA were killed by the Court, which also opined the constitutinality of Social Security. This is how we war now.