The declaration was signed by 56 angry old white guys who had had enough of what the Cousins were doing to them. In seceding from the mother country, these patriots put their lives, fortunes and honor on the line.
Four score and five years later, 11 states invoked the same right “to dissolve the political bands” of the Union and form a new nation. After 620,000 had perished, the issue of a state’s right to secede was settled at Appomattox. If that right had existed, it no longer did.
I have no idea why Buchanan refers to the signers as “old”. The mean average age of the men who signed the Declaration was 44.5. The oldest signer was Benjamin Franklin at 70 (though given his personality his colleagues, and the ladies at the Court of France, would probably have pegged it considerably lower.) The youngest signers were Thomas Lynch Jr. and Edward Rutledge, at 26. Nearly two-thirds of the signers were in their 30’s or 40’s. Unless he accepts the silly notion that anyone over thirty is old (even less true today than when it was in vogue back in the 60’s) calling the signers ‘old men’ leaves rather a false impression.