Extrajudicial detention covers a wide range of situations in which the physical freedom of an individual is constrained or abridged by authority outside what is generally considered an open and legitimate trial process. As well as detention proper, this may also include extrajudicial capital punishment.
Governments and nongovernmental organizations have a range of criteria for detention; see Related Articles for specifics. They usually have different rules for citizens and noncitizens on their own territory. On home soil, they may use national security, police, medical and a variety of other criteria. Some will apprehend citizens or noncitizens outside their territory, either bringing them back or sending them to third countries under extraordinary rendition.
There is no strict rule that states this must be a governmental or quasi-governmental activity, rather than, for example, a neighborhood detaining a drug dealer, but the principle in the Convention against Torture is that torture, in the context of international law, is governmental. In the context of extrajudicial detention, hostage-taking by quasi-governments such as Hezbollah reasonably can be considered within the scope of this article, since such organizations generally seek legitimacy.
Extrajudicial does not equate to illegal, as customary international law has long provided for specific circumstances in which a trial process may not be practical or applicable, including such offenses considered hostis humani generis such as piracy in international waters. The laws of land warfare have accepted as legal, but not civilian judicial, secret and summary handling of "spies" by military law, using a term of art referring to a participant in conflict who conceals his status.  Extrajudicial detention, however, is not limited to military matters or prisoner of war determinations. People can be detailed for reasons related to public health, potential threat (i.e. preventive detention), citizenship, and economic status (e.g. vagrancy).
International law, in this area, has evolved both in military and civil contexts. Perhaps the broadest set of applicable concepts comes from the Universal Declaration of Human Rights, a set of principles, and the first treaty that attempts to codify its goals in a form that can be implemented, the International Covenant on Civil and Political Rights (ICCPR), supplemented by other agreements.
As an example of specific agreements, countries may have public or secret agreements for the subset of detention covered by extraordinary rendition (i.e., as distinct from extradition treaties). Persons affected by them are rarely in their home countries. As a consequence, the Refugee Convention may apply to acts of extrajudicial detention that carry individuals across national boundaries. The Convention against Torture has a provision called refoulement, which prevents the transfer of individuals to a state where they may be tortured. This provision literally applies only where an individual is transferred among nations.
War is an unusual state for a society. As a consequence, early attention was paid to the challenges, even to democratic societies, of the need for special handling military situations. In a number of the military-related situations, there are guidelines for determining combatant status, originally in the Lieber Code, then the Second Hague Convention (1899) and then Third Geneva Convention. Generally outside the scope of extrajudicial detention, but more associated with the battlefield, include captivity, abandonment under conditions likely to lead to death, or summary execution under standards of military necessity.
With respect to civil jurisdiction, there simply is no all-encompassing definition that fits even all democracies, since different countries operate under different legal systems. English-speaking countries tend to be based on common law while French-speaking countries use civil law. Of course, not all countries are liberal democracies. Some do operate under religious law, such as Islamic states that use sharia. Other, totalitarian states do not really have an independent judicial system.
Arguments that the Magna Carta or European Declaration of Human Rights are guiding principles become quite questionable, respectively, when applied outside England or Europe. While the principle of habeas corpus from the Magna Carta certainly is found in common law states around the world, it cannot be considered universal for democratic states that do not use common law; the Universal Declaration of Human Rights is not based on any specific legal system.
Jurisdiction becomes a major issue. While it is widely accepted that the trial of major Nazi war criminals at Nuremberg was ethical and within the context of world justice, many Nazis would not have agreed they were being tried by a legitimate process. While the idea of banning aggressive war had been agreed in the Kellogg-Briand Pact, that treaty did not prescribe enforcement mechanisms. Crimes against humanity had not been defined, by international agreement, before the defendants committed them. While the arguments were rejected by the Tribunal, some of the defenses were based on the arguments of following superior orders, especially in the context that the Nazi Fuhrerprinzip made any decree by Adolf Hitler legal.
International law is oriented toward nations; non-national fighting forces were simply not considered. Many recent or current issues against those deemed terrorists, are focused on people whose allegiance is to other than recognized states. Making the matter even more complex is that working international definitions of terrorism focus on attacks on civilians; is an attack, even if clandestine, on a purely military facility properly terrorism? Were suicide attacks on military targets, as by the Japanese kamikaze, terrorism?
There is no simple answer if extrajudicial detention applies when a competent court in one country orders the arrest of a person not in that country, and that person is obtained not through international extradition, but through a clandestine operation such as the apprehension of Adolf Eichmann.
There is an evolving and controversial concept of universal jurisdiction, certainly not accepted everywhere. As in the case of Augusto Pinochet, while a Spanish court issued a universal-jurisdiction arrest order, on the basis of crimes against humanity, and extradited Pinochet from Britain, the Chilean courts did not agree to the detention of their citizen.
Another complexity is whether extrajudicial detention can be construed to include barring classes of persons to enter the borders of a country. Denial of border entry, for public health reasons, is far more common than mandatory quarantine inside countries. While the Universal Declaration of Human Rights guarantees, in article 13, "Everyone has the right to leave any country, including his own, and to return to his country," and that "Everyone has the right to an effective remedy by the competent national tribunals for acts violating the fundamental rights granted him by the constitution or by law,"  it is not clear if quarantine regulations have a requirement for tribunal review. In large-scale public health emergencies, it may well be logistically infeasible to hear appeals.
National and local issues
Looking at this problem only through the lens of things related to international acts, even if poorly defined such as "terror", ignores a number of contemporary practices that have aspects of extrajudicial detention, or perhaps special legislation applied on top of judicial action.
Round up the usual suspects
It is not at all uncommon, in essentially democratic countries, to have police sweeps that take prostitutes, into temporary custody, with charges never filed; the nature of their work makes them visible as a political statement of being "tough on crime", on a "zero tolerance" or "broken windows" theory of urban policing, or simply because they are easy targets.
Many police do have either the right to detain for a limited period of interrogation before charges must be filed. In other situations, the police may not be legally empowered to detain, but the color of authority, or indeed actions ignored by supervisors, take place.
Belgian law, for example, allowed imprisonment for vagrancy, a case that rose to the European Court of Human Rights. 
Under the current Canadian Quarantine Act, "A peace officer may, at the request of a screening officer or quarantine officer, arrest without a warrant and bring to a quarantine officer any traveller who the peace officer has reasonable grounds to believe has refused to be isolated or refuses to comply with a measure" There is a basic review process by a review officer and the Minister of Health, and, in individual cases, the health authorities are expected to request a court order. There is, however, an emergency provision where a Governor in Council may authorize the barring of entry into Canada of classes of people coming from suspected areas of infection. Denial of border entry is far more common than detention inside countries.
In Enhorn v. France, a man positive for HIV, had kept some of his medical appointments but had missed others, was detained by the order of a public health officer, arguing that he presented a risk of infecting others. Part of the evaluation was that he was initially judged to misuse alcohol and have personality disorders, but was neither legally addicted to alcohol or insane. The initial three-month detention was extended to over four years, with a disagreement on his degree of mental illness between his hospital and personal psychiatrist. The ECHR held that this violated Article 5, as it had not been shown that less extreme measures could not prevent the spread of disease by the voluntary act of sexual intercourse, as opposed to a disease that could spread from the mere presence of the patient. 
A matter concerning Poland's "Law of 26 October 1982 on Education in Sobriety and the Fight against Alcoholism (Ustawa o wychowaniu w trzeźwości i przeciwdziałaniu alkoholizmowi ) was appealed to the ECHR. This law defined two classes of persons, those “addicted to alcohol” and those who are “intoxicated”. Being under the effect of alcohol, as determined by police observation, was considered medical and not criminal. The Polish courts had held that a person arrested and confined "is not entitled to bring proceedings challenging the lawfulness of the deprivation of his liberty since, according to Article 206 of the Code of Criminal Procedure, only a person arrested on suspicion of having committed an [criminal] offence may appeal against a decision to arrest him."  In other words, police-assessed, sometimes medically-confirmed, behavior is grounds for extrajudicial detention.
Sometimes involving judicial orders and sometimes not, individuals may be detained based on principally psychiatric rather than a criminal criteria, although there is overlap. Behavior regarded as quite within individual rights in one country may be regarded as mental illness in another.
Medical authorities may also detain persons who are believed, by mental health professionals, to be dangers to themselves or others. It is not uncommon, in the United States, that such a detention is for a relatively short time, such as 48 or 72 hours, at which time the detained patient may demand judicial review. That authority, however, may order involuntary commitment to treatment facilities, and, once an individual is committed, different authorities may make the determination to release.
The defense of "not guilty by reason of insanity" will still, in most cases, lead to detention, but in a mental health facility rather than a prison. One of the challenges here is the sentence is indefinite; one will be released only when deemed "cured", or at least no longer a danger.
Again in democratic countries, an individual may indeed be tried, sentenced, and imprisoned through the judicial system, for sexually-related crimes. In some cases, such as Kansas v. Crane, after completion of sentence, the individual is never released, but is transferred to psychiatric care, which he cannot leave. Arguments here assume that he still has an uncontrollable impulse that either needs treatment, or is not curable of that disorder so the classic rule for psychiatric detention, "danger to self or others", applies, but with more of a compulsive quality than other emotional disorders.
It is not the intent of this article to argue the merits of uncontrollable risk in such cases. Rather, it is the intent to note that the detention is to some extent extrajudicial, as the decision to release, even if it must be countersigned by a judge, rests with medical personnel.
While informal confinement of "madmen" goes well back into history, the twentieth century saw more formal examples of detention by psychiatric authority, although some diagnoses were seen as politically motivated by observers outside the government. In other cases, an individual might be imprisoned through a judicial process, but, at the end of sentence, not released but put into psychiatric custody.
In the Soviet Union, certain kinds of political behavior were regarded as mental illness; many of these issues were studied in Roy Mendevev's A Question of Madness; there could be extrajudicial detention, Soviet Union, psychiatric.
War and security
In English law, the principle of habeas corpus governs custody; this principle extends into the current practice of many common law nations. Agreement more general than common law, however, may first have appeared, in modern times, in the provisions of the Declaration of Paris (1856), establishing guidelines for the treatment of pirates captured in international waters, under the doctrine of hostis humani generis.
19th century and First World War
Both the laws of land warfare, and more general international law began to be codified in the mid-19th century. The Lieber Code was American, but recognized, by the International Committee of the Red Cross, to be a precursor to the Geneva Conventions and Hague Conventions.
Taking of hostages, including killing them for reprisals, was a gray area in international law. It unquestionably was done by the Prussians in the Franco-Prussian War and by the Germans in the First World War. In the Hostages Case in the Nuremberg Military Tribunals, hostage-taking was not strictly treated as a war crime.
Australia detained Russian immigrants, during the First World War, who were suspected of involvement in radical activities. "The situation of the radical immigrant in Australia is different from the American case in terms of sheer numbers, though not necessarily in revolutionary fervour;"  the period just after the First World War and the Russian Revolution of 1917 led to "Red Scares" throughout the West. The "Palmer Raids" in the U.S., named for Attorney General A. Mitchell Palmer, whose deputy was J. Edgar Hoover, apprehended and deported 249 suspected "Bolsheviks", such as Emma Goldman, in 1919-1920.  Palmer wrote "How the Department of Justice discovered upwards of 60,000 of these organized agitators of the Trotzky [sic] doctrine in the United States is the confidential information upon which the Government is now sweeping the nation clean of such alien filth..."
Second World War and aftermath
Beginning in the 1930s, Joseph Stalin began to have possible dissidents arrested by his administrative decree, interrogated by intelligence agencies in the principal goal of obtaining confessions, and, when confessions were available and sometimes not, conducted public "show trials". These trials could not be seen as means of finding truth, as in civil law, but as means of conveying propaganda.
Preventive detention, under various levels of severity, was common. Extrajudicial detention, U.K. detained both domestic security risks such as Sir Oswald Mosley, head of the League of British Fascists, and spies under the Double-Cross System.
Inside Germany and occupied territories Gestapo had unlimited and independent powers of arrest and imprisonment. Further, in occupied territories, there were several orders to be followed by their military, directing extrajudicial detention or summary execution of civilians considered threats to their forces. One, the Night and Fog Decree, was intended to intimidate through disappearance; it was used more on the western front. The Barbarossa Jurisdiction Order prescribed summary measures in the east.
While in a far less severe regime than that of the Gestapo, the United States extensively detailed both citizens and aliens of Japanese ancestry, who lived on the West Coast. Ironically, the unit of the U.S. Army, most highly decorated for valor for a unit of its size, was the 442nd Regimental Combat Team, recruited from Japanese-Americans in Hawaii and a limited number from the mainland. More selective detentions were made of people of German and Italian ancestry, who were usually either noncitizens or had clear affiliations with groups giving allegiance to an enemy group.
Soviet security organizations frequently detained, and sometimes executed, leaders of rebellious satellite countries, such as Imre Nagy and Pal Maleter, as a result of the 1956 Hungarian revolution. Internally, the Soviet Union made arrests both by the Organs of State Security, and in the context of political psychiatry.
Under Operation Condor, a collaboration among military dictatorships of South America that began in 1975, there was systematic use of "disappearance" as a means of both eliminating perceived threatening individuals and suppressing dissent among people who became known as the "Disappeared ones" or Los Desaparecidos. 
The time of counterterrorism
In this section, dealing with principally 20th century events, there is no attempt to say which side is right, merely what governments did. No sympathy for either side is implied by the saying "one man's guerrilla is another man's freedom fighter." As opposed to the previous section on Cold War matters, this section focuses on activity by non-national groups, as opposed either to popular revolutions or individual dissent.
A substantial number of countries, democratic and not, have used extrajudicial detention for perceived insurgents and terrorists. The International Covenant on Civil and Political Rights (ICCPR) forbids arbitrary detention, but has some room for national emergencies, allowing administration as well as judicial detention. "...the question of whether a given deprivation of liberty is arbitrary is harder to assess with regard to administrative detainees than it is with regard to normal criminal defendants."
Well before the contemporary focus on terror, complex situations arose with the U.K. and pre-independent Ireland, and particularly in Northern Ireland.
A U.N. Working Group on Arbitrary Detention has established guidelines, including the idea that any detention based on belonging to an "illegal organization" violates the principle of freedom of associations. In contrast, see the International Military Tribunal (Nuremberg), which tried a number of organizations for illegality. The Working Group cited Egypt, Israel, and Saudi Arabia as improperly detaining for such membership. 
Geneva Conventions Additional Protocol I addresses the granting of prisoner of war status to combatants who do not fight in uniform and may mix with civilians. Many countries are opposed to this extension, especially major powers.
There is also the issue of hostage-taking by quasi-governments (e.g., Hezbollah) or parts of governments that may not have widespread recognition, such as the Taliban or Hamas. This remains unclear in international law.
Detention has commonly been a matter of national jurisdiction. On a regional and international basis, however, some review organizations exist. Some have fairly wide acceptance, some with restriction, and some very little. Their justification ranges from "victors' justice" to widely ratified international agreements.
There is no judicial body explicitly responsible for enforcement of the Universal Declaration of Human Rights (UDHR), which, in any event, is more of a framework than a set of enforceable laws. The International Criminal Court is principally a court for hearing primary accusations of crimes against humanity, rather than to review national decisions.
In Europe, review is addressed by the European Convention on Human Rights (ECHR), which is a European implementation of the UDHR. It provides for a European Court on Human Rights.  While the ECHR has influenced legislative change, as with the Belgian vagrancy laws, it is not accepted by all European nations, much less nations outside Europe.
In the Belgian case, there were technical issues of jurisdiction of the ECHR court; one legal position was that the role of the Court was to deal with the rights of society rather than individuals, so there were issues of having advocates for individuals argue before the court. Subsequently, however, the Polish sobriety arrest case was argued for an individual, although precedent would be established.
Article 5 of the ECHR is a key position on extrajudicial detention in Europe. It states "Everyone has the right to liberty and security of person. No one shall be deprived of his liberty, save in the following circumstances and in accordance with the procedure prescribed by law". It prescribes both standards for legality and procedural guidelines, which include thorough recording of the event.
- Instructions for the Government of Armies of the United States in the Field (Lieber Code), International Committee of the Red Cross, 24 April 1863, article 88 Cite error: Invalid
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- United States General Assembly ((entry into force) March 23, 1976), International Covenant on Civil and Political Rights, United Nations High Commissioner on Civil Rights
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- Universal Declaration of Human Rights, United Nations, articles 13, 8
- Jennifer Block (November 18, 2003), "Street Sweeping: Bloomberg Plan Sends Prostitutes Cycling From City Jails to Local Corners", Village Voice
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