Related Rule
United Kingdom of Great Britain and Northern Ireland
Practice Relating to Rule 100. Fair Trial Guarantees
Section N. Non bis in idem
The UK Military Manual (1958) provides: “No internee may be punished more than once for the same act or on the same count.” 
United Kingdom, The Law of War on Land being Part III of the Manual of Military Law, The War Office, HMSO, 1958, § 71.
The manual also states: “A prisoner of war may not be punished more than once for the same act or on the same charge.” 
United Kingdom, The Law of War on Land being Part III of the Manual of Military Law, The War Office, HMSO, 1958, § 204.
The UK LOAC Manual (2004) states in its chapter on the protection of civilians in the hands of a party to the conflict:
In the case of penal offences relating to the armed conflict, the basic principles of natural justice must be observed … These principles include the following: … no one shall be prosecuted or punished by the same Party for an offence in respect of which a final judgement acquitting or convicting that person has been previously pronounced under the same law and judicial procedure. 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, § 9.6.
With regard to prisoners of war, the manual provides: “A prisoner of war may not be punished more than once for the same act or on the same charge.” 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, § 8.34.
In 2004, during a debate in the House of Lords, the UK Attorney General stated:
My Lords, the noble Lord first asked whether soldiers were being put in double jeopardy, because he said that after being acquitted by a court martial they might be subject to a criminal trial. Let me put his mind absolutely at rest. There is no question of that. The doctrine of autre fois acquit, as it is known, applies. If a serviceman is acquitted by a court martial he will not stand trial again before a criminal court. A quite different situation arises where there has not been a trial in the court martial at all. 
United Kingdom, House of Lords, Statement by the Attorney General, Hansard, 25 October 2004, Vol. 665, Debates, col. 1058.
In 2003, in its sixth periodic report to the Human Rights Committee, the United Kingdom stated:
Article 14
Retrial for Serious Offences (Double Jeopardy)
538. The Law Commission reported on “Double Jeopardy and Prosecution Appeals” in 2001. Part 10 of the Criminal Justice Act 2003 reforms the law relating to double jeopardy, by permitting retrials in respect of a number of very serious offences, where new and compelling evidence has come to light. The Government considers that these provisions are consistent with article 14(7) of the Covenant, as interpreted by Human Rights Committee General Comment No. 13 of 13 April 1984. 
United Kingdom, Sixth periodic report to the Human Rights Committee, UN Doc. CCPR/C/GBR/6, 18 May 2007, submitted 1 November 2006, § 538.