Caporegime
If is has a military to back it up a region, area, principality, kingdom, or whatever can just declare itself independent. Pretty much how it's worked in a basic way since nations began. Catalonia doesn't really have a fighting force though.
If you are suggesting a civil war then I guess they have people...but we’ve been there in the past and that’s why we have a unified Spain? People have lived in peace since so what does independence really gain?