Is there a nut on the back side of the rivet? if not, then sharpening them may not be realisitic. Those are Either Early Aviations snips, or cheap imitatins. Aviation snips normally have a compound leverage mechanism, and can be dissasembled for sharpening.
Sharpening takes a fine grit grinder, preferably lower speed, and a special file to reset/re-cut the "teeth" so they grip the metal being cut. That file is normally either special order, or you have to go to a specialty store that supplies sheet metal workers their tools to get them. I've never seen that file in a regular hardware store, and I don't remember it's formal name off the top of my head... Checkering file?
