A federal judge Wednesday put a hold (.pdf) on parts of California's just-passed Proposition 83, which sets limits on how close a former sex offender can live to a park or school, and requires all ex-cons convicted of felonious sex crimes to be monitored electronically for life.

The ruling, by San Francisco judge Susan Illston (familiar to 27BStroke6 readers for her judicious handling of my FOIA lawsuit against DHS), only addresses the provisions in the law that say sex offenders can't live within 2,000 feet of a school or park where children regularly gather.

That's probably the most bone-headed section of the ill-conceived law, since it'll have the effect of pushing sex offenders out of cities and into the suburbs, where there are more kids. But the constitutional reasoning Judge Illston applied should also strike down the electronic monitoring provision, once its challenged.

The ruling came in a hurriedly-filed lawsuit by an anonymous ex-sex offender who provided evidence that he'd "been a law-abiding and productive member of his community in the years since his conviction," and would now be forced to move from his home by Prop 83.

Illston found the law likely violates the Consitution's Ex Post Facto Provision, which prohibits the state from retroactively criminalizing prior conduct, or, in this case, retroactively changing the punishment for a previous crime. She also found the law likely violates due process.

While not framed as "punishment" in the text of the proposition, forcing people to move from their homes is "punitive by design and in effect," she wrote.

California's attorney general, Bill Lockyer, thinks the law is constitutional, which only shows he hasn't read the law, or hasn't read the Constitution.

Forcing ex-offenders to wear GPS ankle bracelets for the rest of their lives is also clearly punitive. But the plaintiff in the lawsuit didn't challenge that part; it only applies to offenders who've done time, so it's possible it didn't cover him.

Someone will certainly challenge it, though, and that section of the law will also be shuttered for past offenders. You can't reach back in time and re-sentence someone on a offense for which they've already been judged.

The law will probably stand with respect to new convictions. That's unfortunate. The state is going to foot the bill for 24-hour monitoring of thousands of people for the rest of their lives, without ever taking a look at the details of their offense.

A guy convicted of having sex with his underage girlfriend as a teenager will still be wearing his GPS ankle bracelet when he's in his 70s. So will a repeat exhibitionist. Not your problem? Wait 'til you're stuck behind them at the airport metal detector.

How many serious offenders could be caught if the resources we're about to spend monitoring geriatric flashers went into law enforcement instead of gadgets? A smart law would let judges decide who warrants lifetime electronic monitoring, not voters.