In cases of invasion, grave disturbance of the public peace, national disasters or any other exceptional circumstance which may place society in grave danger, a government may suspend throughout the nation or in particular places, those rights that may constitute obstacles to re-establishing the anterior situation. Although states of emergency are legally intended to be as short as possible and not directed against any particular individual, they are often misused by government authorities who use them as legal pretexts to violate human rights. Special powers tend to facilitate abuses such as arbitrary arrest, torture, 'disappearances' and extrajudicial executions. Suspects can be held on vague suspicions; crimes against the state are given broad, elastic definitions. The suspension of habeas corpus and other legal remedies, trials of political detainees in military courts, as well as the suspension of the rights to strike or of assembly may be alienated under states of emergency. In some countries no formal state of emergency is declared, prevailing conditions are nevertheless tantamount to an emergency; that is, the constitution is suspended, parliament dissolved, all political activity banned and various special measures taken affecting the rights of prisoners and detainees.