Salt Lake City is issuing warning citations to anyone offering a car-ride service without a business license—and yes that means the drivers of the pink mustachioed cars that recently hit Salt Lake City streets.

San Francisco-based Lyft is a booking service that connects ride-seekers to local drivers through a smart-phone app. The drivers use their own vehicles, which can be identified by a large pink mustache on the grill. The company launched its program in Salt Lake City about a week ago.

While it’s become fairly popular nationwide as an inexpensive taxi-alternative, city governments are wrestling with how the model fits into existing ground transportation rules and regulations.

Art Raymond, a spokesman for Salt Lake City Mayor Ralph Becker says drivers are operating illegally.

“So we’re letting these individuals know they’re out of compliance, what they need to do to come into compliance and of course they have a period of time to respond to that,” Raymond says. “And if they continue operating after they’ve been issued a warning they’ll receive a citation.

Raymond says Lyft has not responded to city’s requests for a meeting. A spokesperson for the company told KUER, the peer-to-peer business model doesn’t fall under existing regulations for taxis and for-hire vehicles.

A Lyft driver received a warning citation last week at a Salt Lake City Airport terminal for operating without proper insurance, a business license and other items required by the city and the Transportation Security Administration. Raymond says city officials and council members would consider changes to existing laws.

“We’re not by any means declaring that there is no way for us to accommodate this new business, but those changes take time,” Raymond says. “Certainly, the first most essential step is a conversation with this new company to find out what their goals are for Salt Lake City and to figure out a solution.”

The issue has caused consternation in other cities like Houston and New Orleans. Most recently Kansas City Mayor Sly James took to Twitter to complain about the company’s unannounced arrival in his city.