Some social organizations, such as civil rights groups, human rights organisations, legal aid centers, students' unions, teachers' federations, trade or workers unions are also undone and those who persist with such activities may be killed. Dictators often rewrite an existing constitution or put in place a completely new one. This makes their power constitutional (which then cannot be disputed). Dictators then maintain their rule with state terrorism, which normally involves a secret police, death squads, random or night curfew, indefinite arrest without trial and a network of torture centers and concentration camps. Some dictatorships create a fictional (or non existent) internal (inside their country) enemy which they claim to be at war with to justify (give reason for) their use of much military violence against their people. 