We already have enough biometric documentation of people in the United States. Fingerprints and retinal scans for everyone entering the country is only a hairs breadth away from those for every citizen. Any law passed on immigrants is on the front porch of being passed for US citizens, that's why we as Americans must extend to them every right which we hold dear when entering our country. If not, it gives cause to government to do the same to us as we do to them.