Terrorism Act (2000) - extended detention limit to 7 days without charge for terrorism suspects. The broad definition of terrorism allowed police to legally stop and search a Ph.D. student and journalist protesting an arms trade fair in Canary Wharf.
Regulation of Investigatory Powers Act (2000) - allows government full surveillance powers of all kinds of communication. On average, about 30 warrants a week are issues.
Civil Contingencies Act (2004) - allows government, in times of "emergency", to deploy armed forces in any part of the country during peacetime. Also allows property to be confiscated without compensation.
Anti-Terrorism Crime and Security Act (2001) - in response to 9/11, this piece of legislation allows the government to indefinitely detain foreign nationals suspected of terrorist activities without trial.
Terrorism Act (2006) - following the 7/7 bombings, this allows people suspected of terrorist activities to be detained without charge for 42 days.
R v Incedal and Rarmoul-Bouhadjar (2014) - was going to be the first trial held entirely in secret. The Court of Appeal of England and Wales ruled that the names of the defendants and the outcome must be made public, but the rest of the details will remain in secrecy.