Uh-hunh. I don't know what country you're in, but in mine the government has to actually conscript you to put you in the military against your will and you actually have to be one of their citizens for them to do that. Most of the Companions in the game are not Grey Wardens, not part of the Ferelden military and your character for whatever reason is not inclined to conscript them. Morrigan in particular was never anything other than a fugitive from the law (and barbarian) who was useful to you for a time. Unlike Sten, Zevran and Wynne, she swore no oaths of service and made no promises or bargains. She isn't even really a Ferelden subject, seeing as how she lived in the Korcari Wilds with Flemeth and the Chasind, none of whom were actually under the control of the Ferelden crown. Every moment she drew a free breath she was committing a crime in Ferelden. Expecting her to automatically obey your orders and become a soldier in your army is like a 19th century American expecting every random Indian to join up and fight in the Civil War "because it's their duty as a citizen". No, no it isn't because they aren't.
It doesn't matter,
if you're in a nation and you disobey to the authority
(especially the very highest authority) you commit treason on that nation, you commit a crime against that nation,this work with everyone Morrigan included,until she is in Ferelden territory she is bound to obey like everyone else to the highest authority,if she doesn't wish to commit a crime.
It doesn't matter if someone do not consider themselves as citizen,in this specific case they have even less rights in the country not more.
As i said disobey during a war to the highest general is treason,high treason, citizen or not.
This is why the title of General have immense power.
You're not the champion of a city,you're not the inquisitor of a religious organization,
you're an high general of a nation in charge in time of war ,no one is allowed to disobey to your orders due to your authority especially non citizens,doing this is high treason.
punishable by death.
This is why Anora (as bad as may be) has every reason to demand Alistair execution if he wish to leave which was a GW not a member of the ferelden military.because her authority as the Queen represents the will of the nation and everyone as to respect this will until they are in the territory ,as i said this work with everyone,with every companion after the Landsmeet,they are no more equal to you in Ferelden
(aside from the Queen and the King ).
As for your example of the Indians,it doesn't make sense,since it was an invasion who reduced them in that state,their condition is peculiar,they lost their lands and they possess small amount of reserve in which they are independent,but there are complicated bureaucratic cause still opened.