Interesting! I just had a look at the NC ordinance of succession and they definitely mention slavery and enshrine slaves as property but it's all the way down in section 9 a long with a bunch of other rights.
Weirdly there's actually a section banning the import of any more 'negros' (white slaves ok presumably?).
I'm not completely convinced of your point. Did the people of the time consider states rights the issue?