You can become a citizen after illegal entry.
You can adopt a child that entered illegally, even in the USA. It's complicated, but only because it has been made so, for many reasons. Some better, some worse.
This is the Underworld. This is a place where, if there are illegal immigrants (humans), they're in immediate danger of being
eaten by the citizenry. If it was possible at all for humans to be given citizenship, then Sullivan wouldn't have needed to illegally go to the human world, make a contract with humans that he'd only barely get away with due to his Crown status, and he could just say "Iruma is human, but if you eat him, I'll kill you and your entire bloodline". But he doesn't,
he can't.
Narnia's father basically tried to goad Henri into giving his (human) wife and his "otherwise demon" daughter to be experimented on in a secret government led laboratory, with only Henri's status as their "owner" keeping Nightwalker from taking them outright. It wasn't until the literal Acting Demon King had to step in and force the issue shut (sending away Merize, keeping Ameri's status so secret that numerous bribes and deals had to be made), that the last major incident with a human in the Underworld even had it's bittersweet resolution.
I know you're probably going to say, "Sullivan is a Crown, can't he do whatever he wants?" in regards to having his adoption contract with Iruma's parents honored and the boy allowed to stay. And that's the big thing: that is the big elephant in the room. If it was possible for that to happen, it would have happened already. But it didn't. And there's probably a big reason for it, that not even a Crown can overrule it.
Underworld's rules /= human world's rules on naturalization of illegal immigrants.
That doesn't make it a law.
It's rare enough that there's no need for one to have been drafted before Narnia.
Before, they didn't have to humans (in Narnia's eyes) that are living outside of containment of Border Patrol:
Iruma with Crown Sullivan, and Ameri with Crown Henri.
Before, they didn't have humans earning rankings, both high enough that they'd qualify for graduation before the end of each of their first years.
Before, they didn't have a number of powerful figures circling around them, including some of the 13 most politically powerful demons in the whole Underworld. Asmodeus, Mephisto, Barbatos, Azazel, Sullivan.
There wasn't a law. That's why Narnia is pushing for that law to be made more than just unstated policy. A law that would supersede the objections of those powerful demons that Iruma and Ameri's circles of influence and protection.
His parents put him up for adoption.
The exchange of funds would make it trafficking in the human world, but they teach you how to kill and torture in school, here.
Things be different.
And this affects the Border Patrol's rules... how? Why the fuck would they care that some humans didn't think that they made an illegal deal with Sullivan.
Yes, this is the Underworld, where "things be different". That's why you thinking of Iruma being made a citizen based on real world scenarios shouldn't apply either.
The bad guys are part of the what patrol? hmm?
Their uniforms resemble what other group?
Keep in mind that Nishi is clearly Jewish. (I have impeccable Jewdar. I can watch a film knowing nothing and know if the writer or director are Jewish. It doesn't matter a person's genetics. We can find each other. I have seen people of various colours, made eye contact, and we both know. "Sup!" bow, smile, move on.
A podcaster was once asked "what do you look for?"
"...We look for someone who looks like they're looking for someone."
Point is I was pretty sure, and the Many-ears arc forced me to believe my hopes, much like Clara's mindscape adventure making the Love Trio clearly A THING. I hadn't dared to dream. They went on a date and shared a drink with a heart in it. It made me so bloody happy.)
I'm not going to say that Nishi isn't part of Japan's relatively small Jewish population, because I don't know that. I know that the rankings are based on the Jewish alphabet. I know that the Demon language is basically Japanese that's written to look like Hebrew lettering. I assumed that it's done because Nishi wanted to tie King Solomon and the demons of the Ars Goetia into the setting, complete with name dropping the human as part of the Demon King's prophecy.
And while I can't say with absolute certainty that Nishi based Border Patrol's fervent rule to expel outsiders on Japan's historical isolationism that had them banish or exterminate outsider "heretics" as opposed to any commonalities between any groups in the USA or in 1930's Germany... I know which one I would say it much more likely.
I'll just say it, I find your statements that Nishi made the manga as a statement on real world politics just as ludicrous as the former admin of the Silent Hill wikia that said the developers of the first 4 games were "trying to wake people up" about "the sins of America" that involved satanism and circumsion conspiracies.
Now go read the Many-ears arc again, and tell me Nishi doesn't make political statements.
I agree it's a political statement. I'm just saying it's not based on any specific incident, but more of how the powerful keep a minority underfoot and beholden to enrich themselves, which is a tale as old as humankind itself.
I get the feeling that someone in the comments might be a bigot....
Edit: Their counterpoint?
"UR DUM"
So I'm a bigot because I gave you Dumb reactions? Get the fuck over yourself. I'm anti-ICE, anti-N**i, anti anti-Semitsm. I called your statements stupid, because they're stupid, not for any other reason.