Extrajudicial detention, Soviet Union
Through much of its existence, there were extensive Soviet extrajudicial detention processes, or detention as the result of show trials with only a passing relationship to generally accepted juricial norms. While the names varied, the Organs of State Security, such as the KGB, usually had detention, or even execution, authority.
Particular periods, such as the Great Terror or Stalinist purges of the 1930s, have peaks, but prison camp, not always as a result of formal trial, go far back into pre-Soviet Russian history.
Some of the more recent extrajudicial domestic detentions were under the rubric of punitive psychiatry, or the medicalization of dissent.