This was a book I read in the UK in the early nineties (question inspired by this one:- Apocalyptic fantasy novel set in San Francisco)
On a future planet, or maybe an engineered hollow world, is a community of artists, sculptors and suchlike.
The iron fist authority from elsewhere takes over so the arty people do a non violent fightback.
They use sleeping gas on barracks and, when the soldiers wake up, they have DEAD written on their foreheads with indelible marker that takes several months to fade.
This happens to officers and governors also, some two or three times over the months.
Eventually it breaks morale and lots of the community get released from internment camps and death cells.
Hardback book but I can't envisage the cover.