Prof. Steve Saideman's post on how countries react to secessionist movements elsewhere cites some scholarship, including his own work and Jonathan Paquin's 2010 book on U.S. policy toward secessionist movements, but the post doesn't offer much in the way of a substantiated argument on a couple of points, or so it seems to me. Saideman asserts that a key factor is ethnic ties (as argued in his book The Ties That Divide), and he also says that when ethnic ties are absent, strategic interests will matter. But he pooh-poohs precedent and norms, declaring himself to be a "precedent-skeptic" and a "norm-skeptic."
Maybe the reason for this skepticism is made clear in his book and articles, but it doesn't really appear in the post. It seems reasonable to me to suggest that the territorial-integrity norm (which I believe is a real thing, continuing disagreement from some readers notwithstanding) would imply a baseline of opposition to most secessionist movements most of the time. And I would guess that if one surveyed all the secessionist/separatist movements active in the world today, one would find relatively few of them enjoying much support from states/governments. Certainly I'm not denying that ethnic ties matter in this context (not having read The Ties That Divide, it would be extremely rash of me to do that), but it does seem to me that a flat statement that one is a "norm-skeptic," with the subtext "if you want to find out why, you'll have to read my book," is not all that helpful. But maybe the evidence Saideman has in mind does not lend itself to summary in a sentence or two, in which case the flat statement is somewhat more defensible, I suppose.
ETA: This forthcoming book also takes an approach to secession that appears, according to the publisher's summary, to be 'norm-skeptical.'
Note: Post edited slightly after initial posting.