I don't have a dog in this fight but having been a soldier for 30 years allow me comment.
Being a soldier you accept what soldiering entails including death and disablement, irrespective if you are a citizen or not of that country. However, being a soldier your are naïve in trusting those in authority with matters not to do with soldiering, as you trust your comrades. Believe me, nothing prepares and ex-soldier for the lack of trust soon apparent outside the military. That is where the problem lies.
Every country has its citizenship requirements you must meet to be a citizen. The responsibility for a soldier to meet these requirements doesn't really fit in anywhere, except in the individual himself. On the one hand you have the trust in the organisation [military] to ensure you meet the requirements, on the other hand the individual's responsibility to comply. They should meet in the middle, but if the individual doesn't comply the organisation can't really force him to. This should be an administrative matter included in the induction of all non-citizens into the military, to be finalised when his service terminates.
So without knowing the facts of the matter it might be easy to judge. Probably the truth lies inbetween somewhere.