Like I said, the federal government would handle screening. States just admit a number of people, they don't vet them- the fed has primacy there because of national security and immigration control. Regardless you can replace Syrian with Mexican and probably should. I only said Syrian refugees for the sake of variety.

But again, as a national security concern it isn't a problem. As long as the number of state green cards is less than the number of visas granted, a terrorist will be much more likely to get a visa and overstay it if necessary.