Way back "in the day" of the Internet (1995-1998?), there was a case
in California in which a couple of boys got bad vibes about a neighbor.
They were savvy enough to check online state sex-offender registries...
and found their neighbor on the Texas state website.
(IIRC, Texas even had photos of some of their badboys on the Internet).
Back to Texas the perv went.
BUT, the reverse was not true for a long time. IIRC, even a few years
ago you had to go to the local police and try to pry information out
of them about suspected sex-offense convicts in your neighborhood.
I figure too many fruitloops in power in CA (Hollywood, SF) managed
to keep registries repressed in CA. Hopefully that's on the way out.