Why In-N-Out Is Suing a Delivery StartupThe West Coast fast-food chain says it repeatedly asked DoorDash to cease selling its dishes.

Popular West Coast burger chain In-N-Out has filed a lawsuit against delivery startup DoorDash for delivering its burgers, claiming it has asked the delivery startup repeatedly to cease selling its dishes.

"We have asked DoorDash several times to stop using our trademarks and to stop selling our food," the restaurant's general counsel Arnie Wensinger told CNBC, in an email. "Unfortunately, they have continued to prominently use our trademarks and serve our food to customers who believe that we are responsible for their delivery. Prior to filing the lawsuit, we tried contacting them several more times but they never responded to our phone calls or letters."

He noted that DoorDash has been using its food and trademarks in a way that suggests the companies have a partnership.

Asked for comment about the suit, a DoorDash representative told CNBC, "DoorDash uses its innovative logistics technology to deliver the very best food and products in neighborhoods across the country. While we have various relationships with different merchants, we are proud to help people get their favorite food delivered directly to their door."

DoorDash currently delivers meals in more than 250 cities and has partnered with national chains like 7-Eleven and Taco Bell.