. . .

—“You’re in a position of power in a fictional state, tasked with designing your own variant of the Nuremberg laws, as well as immigration policy. What’s the required vetted minimum IQ for migrants and citizens reaching the age of majority, among other requirements in maintains a viable polity?”—

It depends upon two factors:

a) a relative measurement: your existing median. and

b) an absolute measurement: I work with the rule of thumb of approx 106 being the line of demarcation between those who can solve problems (fix machines, learn from manuals rather than instruction) and those who cannot.

I don’t see any reason why you’d immigrate anyone who wasn’t a full standard deviation above your mean. In that case, i’d say 115 if the person has money and is of good character. Above 122 regardless of money. Above 130 and of good character they are going to contribute.