You're a police officer. You stop a car with expired tags. There's a driver and two passengers. You ask the occupants whether any of them is on probation or parole. (The opinion doesn't say what prompted this question, but I've got a pretty good idea.) The passenger says, yeah, he's on parole. He's also twitchy, nervous, and appears under the influence of narcotics.
You go over to the passenger's side of the car to talk to the parolee. At which point you notice several folded bills stuffed in between the right passenger door and the weatherstripping of the window. You ask the passenger -- and this question seems pretty darn reasonable to me -- "Why is there money sticking out of the window?" He says he doesn't know.
So you unfold the bills and look at them. Promptly realizing that several have the same serial numbers. Which leads you to ask for consent to search the car, which you get, which leads to the discovery of two suitcases full of counterfeit $20 bills and counterfeiting equipment and ultimately a confession.
Sounds like pretty good police work to me. When the passenger says "You didn't have probable cause to unfold the bills," I agree with the Ninth Circuit that he's wrong. There's a parolee who's nervous and under the influence and money in a totally weird place that no one claims is theirs. Nine times out of ten that's drug money or counterfeit. There's a crime afoot. It's cool to unfold -- or even sniff (which the officer didn't do, but I would have) -- the cash.