Since the early 1970s, extrajudicial punishment attacks have been carried out by Ulster loyalist and Irish republican paramilitary groups in Northern Ireland. Attacks can range from a warning or expulsion from Northern Ireland, backed up by the threat of violence, to severe beatings that leave victims in hospital and shootings in the limbs (such as kneecapping). The cause of the attacks is disputed; proposed explanations include the breakdown of order as a result of the Northern Ireland conflict (c. 1970–1998), ideological opposition to British law enforcement (in the case of republicans), and the ineffectiveness of police to prevent crime.