anyone can make an arrest, but campus police et al can't shoot you legally as the government police can, they can't call in other branches of government like swat or air support or even the military, they can't take you to jail, after an arrest they need to call the real police. There's a big difference between campus police which are benign and the regular government police. sometimes (as at UC Davis) the campus police get ahead of themselves and start acting like the real police, but thankfully they can be reigned in, unlike the real cops who can do whatever they want and get away with it.