Senator Dianne Feinstein makes an implausible undercover agent, which made her recent experiment in black-market-document procurement all the more persuasive. The California Democrat decided to find out for herself just how easy it would be to get a fake green card and driver's license. So she traded her Hermes scarf for some urban camouflage -- in this case, a gabardine pantsuit -- and went shopping in MacArthur Park, a crime-infested mini-mall for phony immigration documents near downtown Los Angeles. Never mind that the patrician politician went trailing a swarm of agents in dark suits; the fake IDs were hers for the...

