They are a hotly debated topic in many circles, but are generally accepted in the western world as they are seen as protecting the "greater good".
Mikhail Tukhachevsky and his fellow Red Army officers were tried in secret by a military tribunal, and their executions were announced only after the fact.
In the United Kingdom, one of the most notorious secret courts was the Star Chamber under King Charles I of England in the early 17th century.
The abuses of the Star Chamber were one of the rallying points of the opposition that organized around Oliver Cromwell and ultimately resulted in the execution of the deposed king.
That, combined with the minimal number of requests that are rejected by the court, has led experts to characterize it as a rubber stamp; the former National Security Agency analyst Russ Tice called it a "kangaroo court with a rubber stamp".