Let's get the bad news out of the way first: being a dual national doesn't mean you automatically have special exemption from military service. If you're a Swedish national in the applicable age bracket living in Sweden, dual nationality or otherwise, then you're eligible.
In the case that you have already done some form of military service in another country however, you could get out of it.
“It’s OK to serve in the Armed Forces with dual citizenship. However, the person can only do military service in one of their countries,” the Swedish Armed Forces communication department explained to The Local.
Another detail is that dual citizens cannot be used in combat should conflict break out between Sweden and the other country they are also a citizen of. Again, per the Swedish Armed Forces communication department:
“A soldier with dual citizenship cannot be used in combat in the event of a conflict between the two countries.”
But what impact could serving for Sweden have on your dual nationality? One question being put forward in some expat Facebook groups is whether dual citizens who hold Swedish and American citizenship, for example, could lose their American citizenship if they do Swedish compulsory military service.
The Local contacted the US Embassy in Stockholm to clarify that question, and they referred us to this guidance from the State Department website. It states that revocation of US citizenship could be provoked in certain instances of serving in a foreign military, but that is only the case if the other country is at war with the US:
“Military service in foreign countries usually does not cause loss of nationality since an intention to relinquish nationality normally is lacking. The Department has established an administrative presumption that a person serving in the armed forces of a foreign state not engaged in hostilities against the United States does not have the intention to relinquish nationality.”
So unless Sweden goes to war with the US, your dual US-Swedish citizenship won't be impacted by doing military service for Sweden.
For Australia, it's a similar deal. If you're not fighting for a foreign country at war with Australia or a declared terrorist organization, you’re not going to lose your citizenship. The UK follows similar rules. As does Canada. And Italy.
In France, only those who have acquired French citizenship and have been convicted of treason or terrorism can be stripped of it. In Brazil, doing national service for another country is not a cause for losing Brazilian citizenship.
What about Kiwis? Don't worry, we didn't forget you. “The only way someone can lose their New Zealand citizenship is if they have it removed by order of the Minister of Internal Affairs,” Steve Corbett from New Zealand's Ministry of Internal Affairs told The Local. The main reason for such an order to be issued is if (stop us if you've heard this already) you act against the interests of New Zealand.
To state the obvious, we haven't covered every nation in the world, so it's worth checking with the relevant embassy to be sure, but the rule of thumb for the ones we have checked is that as long as Sweden isn't at war with the other nation you're a citizen of, being drafted by Sweden won't impact your dual citizenship.
In other words, unless Sweden suddenly decides that after more than 200 years without an official war it feels like a return to the days of empire-building, you can probably rest easy.