In the process of deciphering the proposed immigration bill, I found this fascinating site about Biometrics. It's more complicated than it sounds, and not the easy solution that it would seem. I suspect Congress (not a particularly tech-savvy group) just doesn't get it.
Not unlike their understanding of the way this bill strikes Americans.
What is Biometrics? At its most simple, it's fingerprints and photos. The EU has problems with the management of fingerprint data - they're concerned about privacy issues.
Let's not even get into photos - dependence on them is what's behind the fuss over veiled women. If you allow some to opt out, you've eliminated 1/2 of your verification scheme.