Like, say you’re a dual citizen somewhere with a military service obligation. Or you long for adventure in the French Foreign Legion.
You can, as an American, serve in a foreign military doing military stuff!
Because it is not exactly illegal to serve in a foreign militia, but if it’s not the actual gummint army, there are suddenly a lot more technicalities.
Involving the use of explosives.
In, you know, a *country’s actual army.*
In which capacity a foreign militia does not exactly qualify.