WHEN Department of Licenses & Inspections enforcers busted the Buttercream Cupcake Lady's truck last week in University City, it sent shock waves through the cutting-edge gaggle of rolling gourmet-food vendors that roam Philadelphia, broadcasting their locations via Twitter, vending for a couple of hours and moving on.

Philadelphia is a newcomer to the drive-by dining fad that has so overwhelmed New York City streets that there's a freeze on vending permits. In Los Angeles, the city council is currently scrambling to legislatively control the outbreak of unregulated rolling gourmet kitchens.

Right now, Philly's half-dozen roaming trucks include two that sell high-end cupcakes, a farm-ingredients taco truck, Mojo Gourmet Coffee, Renaissance Sausage (@TheSausageTruck on Twitter) and The Dapper Dog (@thedapperdog) - offering wee-hours wieners on wheels.

Kate Carrara, aka Buttercream Cupcake Lady, ran afoul of L&I enforcers when she parked on Market Street near 33rd-mistakenly thinking she was a block outside the University City restricted zone.

L&I Commissioner Fran Burns said that Carrara had the city ordinance on restricted zones and must have known she was taking a chance on confiscation.

But the Cupcake Lady (@ButtercreamPhl on Twitter), who talks more like a New Age flour child than the 35-year-old lawyer-turned-baker that she is, said that the city law is layer upon layer of revisions, and she found it indecipherable.

"Could a lawyer figure that out?" Carrara asked. "No. I'm a lawyer and I couldn't. Maybe a team of lawyers could.

"My husband, Andy, who works for Morgan Stanley, spent hours marking the restricted streets on a city map," she said. "I'm the dreamer. He's the numbers nerd. I think like a flower. He thinks like a computer. We thought we were a block outside the restricted zone-and we still got busted."

Amazing but true: New York City lists all five boroughs of vending-restricted streets in seven, clearly organized, easy-to-read pages. Philadelphia's list is 20 pages of chaos.

Carrara paid a $200 fine and got her truck back but, a week after the bust, said that she is still feeling the incident's "chilling effect."

Despite sticking to LOVE Park, where she has a special permit from Fairmount Park, and to areas outside Center City and University City, Carrara, who has more than 4,300 followers on Twitter, said that "every time I hear a siren, I get all jumpy in the truck and I think, 'Oh, my God, they're coming to get me.' "

Commissioner Burns said that when something like the Carrara bust happens, people think of L&I as the bad guys, but that's not true.

"Like the police, we enforce the law," she said. "We don't make the law. The legislature [City Council] makes the law."

Besides the three city licenses that all food-vending trucks need, Burns said, stationary trucks pay $3,000 a year for a permit to occupy one of the 300 legal spots in Center City or the 100 legal spots in University City.

The Twitter-centric roaming trucks are such a new phenomenon here that the city's laws-which still describe a $300 vending permit for horse-drawn wagons-exist in a different millennium.

"When I first started in June, I didn't know that the law pretty much prohibits roaming trucks from vending anywhere in Center City," said Dave Dilks, 40, owner/operator of Call Me Cupcake, which, like Carrara's truck, sells gourmet cupcakes and was busted by L&I in a less-publicized confiscation last month. (It's @CallMeCupcake on Twitter.)

"So, I was happily vending at 19th and Market all summer, thinking everything's cool, when suddenly, a couple of weeks ago, a police car angled in front of my truck. I thought he was pulling in to get a cupcake."

Another cop car pulled up alongside Dilks. An L&I agent said that he was confiscating the truck.

"I wanted to roam the city of Philadelphia and be an entrepreneur," the sadder-but-wiser Dilks said. "Mayor Nutter talks about being progressive and business-friendly. But the city is still stuck in that old-business mentality."

While he's waiting for a new-business mentality to happen, Dilks sticks to the Temple University area, where he hasn't had any problems.

Tom McCusker, a Drexel University graduate whose Honest Tom's Taco Shop started rambling around town in April 2009, has avoided the wrath of L&I by avoiding what he believes is a primary cause of it: irate rival vendors, who are paying $3,000 a year to park in a designated spot, calling the city to complain about roamers like himself.

"I just try to stay away from all other trucks to avoid problems," McCusker said. "I was up near the Drexel dorms, around 33rd and Arch, for a year and had no problems with the city because I was the only truck up there. Same is true around 18th and Vine, and Broad and Lombard. And I went over the map with an L&I lady to make sure I'm not in a restricted zone."

McCusker said that his farm-fresh gourmet breakfast and lunch tacos, touted on Twitter and Facebook, have attracted their own customer base, so he doesn't need to be in a crowded "hot spot" to sell his food.

He makes his tacos to order in what used to be the Viva Las Vegans truck before it was Honest Tom's.

On Saturdays at 6 a.m., McCusker pulls up at the farmers market in Clark Park, on Chester Avenue near 43rd, buys his taco ingredients from the farmers, and sells breakfast and lunch tacos until he runs out of food.

But even McCusker's hassle-free life as a roaming food truck entrepreneur felt the chill of the Cupcake Lady confiscation.

"Since they took that lady's truck, every day I'm thinking something is going to happen to me," McCusker said. "They give you this list of restricted blocks and the list is so hard to understand that I don't think even they understand it.

"What they should do is say, 'OK, you want to be a roamer? Give us a thousand bucks and you can roam anywhere you want.' And I'd say, 'Here's your thousand bucks.' End of story."