Rather than doing "nothing", it seems me to that he could at least have explained to the people of his country that, "the laws recognize that the South had a legitimate right to leave the Union if the government of such no longer suited their Interests."
YessireeBob, if only Buchanan had simply done that. Welp, he didn't and that set the advent of the internet back by four years.
Sure, because everyone needs the color of the sky "explained" to them from time to time. It's too much to just ask them to read the Declaration of Independence or something.