These weapons are not aimed at rioting factions, but at peaceful marching protestors.
Riot police also used stingball grenades to disperse the crowd. A controversial riot control device, the grenade is thrown at ground level, releasing scores of rubber pellets that cause an intense stinging to the legs within a 15-meter (50-foot) range...
https://www.dailysabah.com/europe/2019/05/01/french-police-clash-with-may-day-protesters-in-parisFrench police clash with May Day protesters in Paris - Daily Sabah
French police clashed with stone-throwing protesters who set fires and smashed up vehicles as thousands of people gathered for May Day rallies Wednesday under tight security.