This is them fighting Catalonian police after their independence referendum!
Even the Spaniards give the Guardia a wide Berth.
Policia Local, are armed Traffic Wardens owned by the Mayor, if you speak spanish you can get away with arguing with them. If you cannot speak Spanish say nothing else you will get a baton accross the head just for being a Giri.
Policia Nacionals are the most professional and not to bad to deal with, as long as you dont argue with them, they are fine and are generally quite helpful.
Guardia were Franco's hench men, thousands of Spanish dissapeared at the hands of them, they still strike fear in most spanish citizens, and residents.
There is absolutely no control, or complaints process against them police in Spain, they can and do, do exactly as they want.
Corruption by them is no where near as bad as it was, but as a Giri, once you have had a beating, you will still get taken to the cash point for a donation by some tho not all.