On Sunday 27 February at 7:15 AM GMT, the BBC reported that: (source)

Ukraine asks foreign volunteers to help
Kyiv says it's establishing an "international" legion for foreigners wishing to volunteer in support of Ukraine. "This will be the key evidence of your support for our country," remarked President Volodymyr Zelensky in a statement issued just now about Ukraine's new "foreign legion".

The use of the word "legion" suggest that these volunteers would become combatants. Would it be legal for European citizens to join such a Ukrainian foreign legion, and take up arms in the Russia/Ukraine conflict? Would they have to wait until their own government formally gives permission to its citizens to join the Ukrainian military (like the Irish/British situation in WWII)? Would they risk being prosecuted when returning home, if they joined now without awaiting such a decision? And what would their status be if they were captured by Russian forces?


In a later article, the BBC quotes the Ukrainian president making the claim that it would be legal for foreign nationals to volunteer:

A more detailed post says foreign citizens are legally allowed to join Ukraine's defences, and that a separate division of fighters is being formed called "the International Legion for the Territorial Defence of Ukraine".

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    Some of the applicable laws are listed on the Wikipedia article for Mercenary#National laws.
    – sjy
    Commented Feb 27, 2022 at 9:15
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    It's unclear what you are asking. Are you asking about anything specific in EU law, are you asking about laws in individual countries in the EU, laws of individual countries in Europe, or any laws and treaties that apply to "many" European counties such as NATO, EU/EEA, etc? Or are you asking about Ukranian, or even Russian law?
    – Peter
    Commented Feb 27, 2022 at 9:18
  • Are you asking about enlisting in the ukraine army as a foreign national? Are you asking if ukraine may have something akin to the french foreign legion? are you asking about foreign nationals working for hire to fight in the war as a mercenary? Are you asking if foreign nationals may join an ukrainian militia (and following the rules and regulations)?
    – Trish
    Commented Feb 27, 2022 at 12:47
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    [...] the Ukrainian president making the claim that it would be legal for foreign nationals to volunteer Just a guess, but probably he was claiming that it would be legal under Ukrainian law. How the country of citizenship of the soldier would react would not be covered by that statement.
    – SJuan76
    Commented Feb 27, 2022 at 14:27
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    It used to be the case in some countries that joining a foreign military caused loss of citizenship. I don't know how many countries have such a law today. In such a country, it wouldn't necessarily be illegal to join the Ukrainian army, but the consequences might nonetheless be undesirable. (Whether fighting in Ukraine would necessary mean joining their military is another question, of course.)
    – phoog
    Commented Feb 27, 2022 at 20:17

3 Answers 3


It’s legal under Ukrainian law for foreign nationals to join their defense forces

Indeed, this is so common it may be considered the default position internationally: the US, UK, France, and Australia just to name a few all allow this.

Generally, it’s usually legal for a citizen to join the army of a foreign state. It is usually not legal to fight for a non-state actor this is where fighters for ISIS are in trouble.

Where issues arise is if they take up arms against the country of their citizenship. That’s called treason and it usually attracts the most severe punishment available: death or life imprisonment typically.

So, as long as you aren’t Russian and are not from one of the few countries that prohibits foreign military service, there are no legal issues.

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    It might have some effects: a German-something dual citizen looses their german citienship if they join the armed forces of the other country unless there is a treaty that this doesn't happen.
    – Trish
    Commented Feb 28, 2022 at 0:49

From the explanatory article in Reuters, looks like it is legal for many countries. US and UK have laws that prohibit citizens from making war against foreign governments at peace with them. However these are claimed by the source to be not always enforced. Germany, Denmark, Latvia and Canada said they would allow their citizens to volunteer.

Because volunteers will be fighting as members of the Ukrainian army, they are unlikely to face charges in their home country over their specific actions in the war, with the exception of prosecution for war crimes or similar.

Russia said that Western "mercenaries" fighting for Ukraine would not be treated as lawful combatants and would face criminal prosecution. From the other side, the "mercenary" status is disputed by international experts. Mercenary is one that serves merely for wages and receives "material compensation substantially in excess of that promised or paid to combatants of similar ranks and functions in the armed forces of that Party". Ukraine only pays a standard soldier salary of $230 per month that is really not a lot.


It might not be legal, under Ukrainian law.

The relevant law is (at the moment) available here. Under Art 1 (and later articles), there is a possibility to be a volunteer of the Territorial Defense Forces of the Armed Forces of Ukraine if you are

a citizen of Ukraine or a foreigner or stateless person who has been in Ukraine legally for the last five years and on a voluntary basis enlisted in the voluntary formation of the Territorial Defense Forces of the Armed Forces of Ukraine

However, as I understand your question, you also mean "A person in Finland who wants to travel and join up": this is not included under the most recent change to Ukrainian law. Art 9-10 address the staffing of the resistance force. There is no other provision for foreigners who don't meet the legal residence requirement.

  • "a person in Finland who wants to travel and join up" is a volunteer
    – Trish
    Commented Feb 28, 2022 at 6:48
  • @Trish: My understanding is the wording is that the foreigner would have had to been in Ukraine for five years to voluntarily enlist in the Territorial Defense Forces of the Armed Forces of Ukraine. Commented Apr 12, 2022 at 0:36
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    The linked law concerns the "Territorial Defense Forces of the Armed Forces of Ukraine" which is the military reserve. It says nothing about whether a foreigner can travel to Ukraine and enlist in the regular army.
    – phoog
    Commented Aug 24, 2022 at 8:44
  • In a live interview a few days ago, Oleksiy Arestovych (a fmr Ukrainian intelligence officer and a current adviser to the office of the president of Ukraine) was asked a question and deferred to legal advice. A few moments later, he quoted a text which he just received stating that a military ID ("военный билет") functions as a de jure residency permit in Ukraine. Presumably whoever gave him legal advice heard the question (which was about a foreign volunteer's residency status). Since a military ID could be issued, one has to assume that the 5-year requirement is not legally in effect.
    – wrod
    Commented Aug 24, 2022 at 21:03
  • @AlexanderThe1st apart from phoog's excellent counter to this whole answer: Only a ukrainian court can decide there the brackets in that sentence should be placed: "(a citizen of Ukraine or a foreigner or stateless person) who has been in Ukraine legally for the last five years" or is it: "a citizen of Ukraine or a foreigner or (stateless person who has been in Ukraine legally for the last five years) ? We cannot know, and I wouldn't be surprised if the vagueness is on purpose
    – Hobbamok
    Commented Oct 11, 2022 at 13:08

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