《瑞典国际人道法手册》（Sweden’s IHL Manual）认为《第一附加议定书》第39条中禁止不当使用国家标志的规定是对习惯国际法的编纂。
《比利时战争法手册》（Belgium’s Law of War Manual）规定了以下不当使用的例子：身着敌方制服开火或参与进攻，以及从缴获敌方的带有徽章的战斗用车辆上开火。该手册规定，“渗透敌方防线以制造恐慌，致使对方将己方士兵误认为是经过化装的敌人而向其开火，或在敌方防线后身着其制服进行军事行动以收集情报或进行阴谋破坏”不被认为是不当使用，
）中，美国驻德国占领区普通军事法庭（the US General Military Court of the US Zone of Germany）宣告因身着敌方制服参加战斗而被指控不当使用制服的被告无罪。法庭不认为德国军官在试图占领敌方军事目标时身着敌方制服是不当的，并且没有证据表明他们在此装束下使用了武器。
然而，对于军用航空器不能使用敌方标志似乎已达成共识。虽然《厄瓜多尔海军手册》（Ecuador’s Naval Manual）和《美国海军手册》（the US Naval Handbook）将这一禁止性规定的适用限于战斗，但《德国军事手册》（Germany’s Military Manual）、《新西兰军事手册》（New Zealand’s Military Manual）和《美国空军手册》（the US Air Force Pamphlet）规定军用航空器不能带有敌方标志。
《加拿大武装冲突法手册》（Canada’s LOAC Manual）认为在空战中若“在军用航空器上使用虚假标识，例如敌方航空器……标识”实施敌对行动，属背信弃义行为。
The draft of Additional Protocol II submitted by the ICRC to the Diplomatic Conference leading to the adoption of the Additional Protocols provided that “when carried out in order to commit or resume hostilities … the use in combat of the enemy’s distinctive military emblems” constitutes perfidy. This provision was deleted from the draft during the negotiations in Committee III of the Diplomatic Conference.
The prohibition on making use of the flags or military emblems, insignia or uniforms of an adverse party while engaging in attacks or in order to shield, favour, protect or impede military operations is contained in other instruments pertaining also to non-international armed conflicts.
The prohibition of improper use of enemy uniforms and insignia is contained in military manuals which are applicable in or have been applied in non-international armed conflicts.
Violation of this rule in any armed conflict is an offence under the legislation of numerous States.
The application of this rule in non-international armed conflicts is also supported by official statements and other national practice.
During the Chinese civil war, for example, the Chinese Communist Party denounced the use of Red Army uniforms by Nationalist soldiers alleging they were used while committing acts designed to discredit the Red Army.
Rule 62. Improper use of the flags or military emblems, insignia or uniforms of the adversary is prohibited.
Volume II, Chapter 18, Section F.
State practice establishes the customary nature of this rule in international armed conflicts. It can be argued that it should also apply in non-international armed conflicts when the parties to the conflict do in fact wear uniforms.
This is a long-standing rule of customary international law already recognized in the Lieber Code, the Brussels Declaration and the Oxford Manual.
It was codified in the Hague Regulations.
Additional Protocol I prohibits the use of enemy flags, military emblems, insignia or uniforms “while engaging in attacks or in order to shield, favour, protect or impede military operations”.
Under the Statute of the International Criminal Court, “making improper use … of the flag or of the military insignia and uniform of the enemy” constitutes a war crime in international armed conflicts when it results in death or serious personal injury.
This rule is set forth in numerous military manuals.
Sweden’s IHL Manual considers that the prohibition of improper use of emblems of nationality in Article 39 of Additional Protocol I is a codification of customary international law.
Violation of this rule is an offence under the legislation of many States.
The rule is also supported by official statements and other practice.
Some practice was found that considers the wearing of enemy uniforms as perfidious.
This does not square entirely, however, with the definition of perfidy inasmuch as enemy uniforms are not entitled to specific protection under humanitarian law, even though the wearing of such uniforms may invite the confidence of the enemy (for a definition of perfidy, see the commentary to Rule 65). Other practice considers it a violation of the principle of good faith.
The Brussels Declaration, the Oxford Manual and the Hague Regulations prohibit the “improper” use of enemy flags, military insignia and uniforms without specifying what is improper and what is not.
The Elements of Crimes of the Statute of the International Criminal Court specifies that it is a war crime to use enemy uniforms “in a manner prohibited under the international law of armed conflict while engaged in an attack”.
Many military manuals prohibit “improper” use without further explanation.
The UK Military Manual specifies that:
The employment of the national flag, military insignia or uniform of the enemy for the purpose of ruse is not forbidden, but the [Hague Regulations] prohibit their improper use, leaving unsettled what use is proper and what use is not. However, their employment is forbidden during a combat, that is, the opening of fire whilst in the guise of the enemy. But there is no unanimity as to whether the uniform of the enemy may be worn and his flag displayed for the purpose of approach or withdrawal. Use of enemy uniform for the purpose of and in connection with sabotage is in the same category as spying.
Belgium’s Law of War Manual provides the following examples of improper use: opening fire or participating in an attack while wearing an enemy uniform and opening fire from a captured enemy combat vehicle with its insignia. The manual states that “infiltrating enemy lines in order to create panic to the point that the adversary starts firing on its own soldiers believing that they are disguised enemies or operating behind enemy lines wearing enemy uniform in order to collect information or commit acts of sabotage” is not considered an improper use,
although these acts may lead to loss of the right to prisoner-of-war status (see Rule 106). Sweden’s IHL Manual explains that:
The prohibition of improper use has been interpreted to mean that enemy uniform may not be used in connection with or during combat, and this has led to great uncertainty in application. During the 1974–1977 diplomatic conference, certain of the great powers wished to retain the possibility of appearing in enemy uniforms, while most of the smaller States claimed that this possibility should be excluded or minimised. The Conference accepted the view of the smaller States here. The rule in Article 39(2) [of Additional Protocol I that the use of enemy uniforms is improper “when engaging in attacks or in order to shield, favour, protect or impede military operations”] can be interpreted to mean that enemy uniform may be used only as personal protection, for example under extreme weather conditions, and may never be used in connection with any type of military operation. Where prisoners of war make use of enemy uniforms in connection with escape attempts, this may not be seen as an infringement of Article 39.
A number of military manuals restate the definition of “improper use” of enemy uniforms contained in Additional Protocol I, namely “while engaging in attacks or in order to shield, favour, protect or impede military operations”.
Upon ratification of Additional Protocol I, Canada made a reservation to the effect that it would only be bound by the prohibition on using enemy uniforms while engaging in attacks but not in order to shield, favour, protect or impede military operations.
Its LOAC Manual restates this point.
Several manuals similarly limit the prohibition to combat operations.
It should also be pointed out that several manuals prohibit the use as such of enemy uniforms.
In the Skorzeny case in 1947, the US General Military Court of the US Zone of Germany acquitted the accused of charges of improper use by entering into combat disguised in enemy uniforms. The Court did not consider it improper for German officers to wear enemy uniforms while trying to occupy enemy military objectives and there was no evidence that they had used their weapons while so disguised.
The United States has stated that it does “not support the prohibition in article 39 [of Additional Protocol I] of the use of enemy emblems and uniforms during military operations”.
There are several examples of conflicts since the Second World War in which the wearing of enemy uniforms was practised, including in non-international armed conflicts.
It cannot be concluded, therefore, that the wearing of enemy uniforms outside combat would be improper.
Several manuals indicate that naval forces may fly enemy colours to deceive the enemy but must display their true colours prior to an actual armed engagement.
However, there appears to be agreement that military aircraft may not use enemy markings. While Ecuador’s Naval Manual and the US Naval Handbook restrict this prohibition to combat, Germany’s Military Manual, New Zealand’s Military Manual and the US Air Force Pamphlet state that military aircraft may not bear enemy markings.
Canada’s LOAC Manual considers it an act of perfidy in air warfare if a hostile act is committed while “using false markings on military aircraft such as the markings of … enemy aircraft”.
The different treatment between ships and aircraft is explained by the fact that it is practically possible to change the flag under which a ship is sailing before engaging in combat, while an aircraft cannot change its marking whilst in the air.