A simple credit check or DMV check will bring in many. Some sex offenders may have simply forgotten. Also, will LE hold the offenders accountable and give them the full penalty for not complying? Sometimes not.
Can't do that, especially if they are illegal. That's the feds job don't you know.
They have constitutional rights you know. Just ask the ACLU.
Soulda, coulda....been deported, but naw.
The laws in most States require offenders to re-apply (make notification) to local law enforcement agencies once a year. Most LE agencies attempt to verify that information twice a year to determine compliance. When an offender is found to be not at the address he previously gave, a warrant is issued for failure to change address. However, once a warrant is issued, the offender is gone, and locating him is very, very difficult. They do not announce their presence, nor attract attention to themselves.