What powers do MI5 have?

Answer 1

MI5 (The Security Service) is an agency of the British Government controlled by the Home Office: the Director reports directly to the Home Secretary (a senior member of Cabinet), and through him/ her to the Prime Minister ("The First Lord of the Treasury"), the Head of the UK Government.

The Security Service is responsible for identifying, monitoring/ evaluating, and (in cooperation with other agencies, especially Police [notably "Special Branch", & Counter Terrorism Branch], Customs & Revenue Service, Immigration Service, GCHQ & MI6, and the Armed Forces etc) countering threats to the security of the United Kingdom and its territories.

To this end, The Security Service carries out a wide range of covert activities (surveillance, "bugging" etc) as well as a great deal of general research and evaluation of real and potential threats.

MI5 officers must operate within the Law, and DO NOT possess any "special powers" per se placing them above the Law. Covert surveillance operations must be authorised by the Home Secretary (who is required to inform the Prime Minister of all such activities, and the reasons for them), and the all party Parliamentary Committee on Intelligence receives regular briefings on current security operations, although usually only in "broad brush" terms.

Arrests of, for example, terrorist suspects are almost always conducted by the Police (Special Branch/ Counter Terrorism etc), and generally "direct action" in other contexts will be conducted by the military, usually Special Forces.

Contrary to public perception, MI5 Officers do not usually engage in "James Bond" style antics. Yes, field officers are trained to defend themselves should the necessity arise, but their role is to "stay in the shadows", watching/ observing, recording, evaluating and collating information, and reporting their findings. A lot (most, in fact!) of MI5's work is information finding/ research, analysis/ evaluation of threats, and reporting it to others who may then act upon it. MI5 is subject to the Rule of Law, and its Director is accountable to the Government of the day, and Parliament, for all that it does.