It makes perfect sense. Differentiating between a good and bad ones is the easiest thing ever.

1. Are they a net benefit to the country's finances? Do they pay more than enough taxes to cover the public services they use and then some. Or are they just a leech on the welfare system and a burden to society in general.

2. Do they integrate well into the society? Do they commit crimes?

3. To whom is their allegeince? The society they live in or the one back home? Do they promote the interests of their own ethnic group at the expense of the natives?

The first two are already available to state, tax, crime, welfare records. The third can be found out with a simple investigation.