This week I had the catalytic converter stolen out of my '07 Prius. Why is it so easy for the thieves to sell these things? If I sell a used battery, I have to show ID and get a check in the mail. Why isn't there some similar law for catalytic converters? —Tina T.

At the risk of besmirching my liberal bona fides, Tina, there's a difference between passing a law and eliminating a problem. Cocaine, for example, is 100% illegal—and yet, I have some right here. Just kidding! (Probably.)

Anyway, now that I'm invincible, I can tell you that Oregon does have laws to foil would-be catalytic converter thieves.

However, in the same way that taking the Sudafed out of my beloved DayQuil did not bring the crystal meth trade to a grinding halt, these requirements are little more than a speed bump for a trade where even a black-market unit can bring $200 or more.

Scrap dealers buying used converters are supposed to get a copy of the seller's ID, a photo of the seller, the license plate number of the seller's car, and video of the transaction itself. Payment by check must be mailed, and only after a mandatory three-day waiting period.

However, plenty of out-of-state scrapyards will happily buy a catalytic converter from you through the mail with just a photocopy of your (or, really, anyone's!) driver's license.

Catalytic converters work their magic by passing emissions through a honeycomb impregnated with a few grams of platinum, palladium and rhodium, in varying proportions.

You're familiar with platinum, so you won't be surprised to learn that it's currently $966 an ounce. However, you might not have known that an ounce of palladium is $2,246—and you probably won't even believe that an ounce of rhodium goes for $13,700.

Given that just two years ago rhodium was a paltry $2,300 (chump change, amirite?), you can see how this dirty muffler-looking thing on the bottom of your car might be more tempting now than ever.

What to do? Well, for a few hundred bucks, you can buy a shield kit to protect your converter—not cheap, but better then the $2,000 to $5,000 it'll cost to replace a stolen one.

Do these kits make stealing your catalytic converter impossible? No. But they do make it more trouble than just stealing somebody else's.

Questions? Send them to dr.know@wweek.com.