Thanks to CrimProf Blog, we see this interesting article from the San Diego Union-Tribune pointing out various problems with Jessica's Law implementation. From the article:
That finding surprises virtually no one in law enforcement. They say the law is vague and has holes, making it nearly impossible to enforce.
For example, the law doesn’t specify whether residence restrictions apply to all convicted sex offenders or only to those who were convicted or paroled after it passed. There are no penalties for violating the restrictions.
Four registered sex offenders, two of whom live in San Diego County, have challenged the residency restrictions, and their case is before the California Supreme Court.
The four men were paroled after Jessica’s Law passed, but their most recent crimes were not sex offenses. Parole officers told them they had to move from restricted areas near schools or parks or be sent back to prison.
I'm not sure I understand the use of the word "vague" here. It certainly isn't in the legal sense. The lack of specific language for retroactivity has been the norm with sex offender laws and that is just a matter of statutory interpretation and constitutional analysis. However, I think the other criticisms of the law in the article are worth noting.