Related Rule
United Kingdom of Great Britain and Northern Ireland
Practice Relating to Rule 65. Perfidy
Section J. Simulation of protected status by using flags or military emblems, insignia or uniforms of neutral or other States not party to the conflict
According to the UK LOAC Manual (2004), “the feigning of protected status by the use of signs, emblems or uniforms of … neutral or other States not Parties to the conflict” is an example of prohibited perfidy “if done with intent to betray the enemy’s confidence”. 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, § 5.9.2.
In its chapter on air operations, the manual states:
Article 19 of the Hague Rules 1923 prohibited the use of false external marks on aircraft. Additional Protocol I now prohibits the use at any time by any party to a conflict of the flags, military emblems, insignia or uniforms of neutral or other states not party to the conflict. The use of flags, military emblems, insignia or uniforms of an adverse party is prohibited “while engaging in attacks or in order to shield, favour or impede military operations”. 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, § 12.10.4.
The manual further states: “Military and auxiliary aircraft are prohibited at all times from feigning exempt, civilian or neutral status.” 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, §§ 12.54–12.54.1.
The UK Geneva Conventions Act (1957), as amended in 1995, punishes “any person, whatever his nationality, who, whether in or outside the United Kingdom, commits, or aids, abets or procures the commission by any other person of, a grave breach of … [the 1977 Additional Protocol I]”. 
United Kingdom, Geneva Conventions Act, 1957, as amended in 1995, Section 1(1).