They might have been Gendarmes – There needs to be a guidebook to the plumage and feeding habits of European cops.
CRS, perhaps? Especially if they were preparing for demonstrations. My impression was (and I'm feeling too lazy to check right now) that the Gendarmerie was responsible more for rural areas, while the CRS handles riots. I remember one of my French lecturers, Dr Dineen, pausing a video just when a CRS cop appears and telling us to study hard and remember that uniform, because if we ever see it we should make ourselves scarce very quickly, the CRS are pretty rough. Or so he said. I agree on the need for a guidebook, though for all the world's various police and security forces. When I first came to China the regular Public Security Bureau cops, People's Armed Police, and army all wore very similar green uniforms. Now the regular cops are in blue, PSB SWAT in black, and although PAP and PLA are still both in green their uniforms are different enough - or perhaps I'm more familiar with them.
In Paris the cops tended to roam in packs
And don't forget the uniformed soldiers strolling the streets in squads, complete with their FN rifles.