Barbara Caruso, spokeswoman for Del Taco, said organizers of Anaheim's Kush Expo never sought permission before putting the fast-food chain's logo on the convention's promotional materials, the Los Angeles Times reported Friday.
"It's unacceptable for companies to use our logo without permission and they didn't have permission," Caruso said.
Taco Bell spokesman Rob Poetsch expressed a similar sentiment.
"We have a longstanding policy that prohibits other businesses from using our trademarks, and we did not give them permission to do this," Poetsch said. "We were in the process of contacting them to take down our trademarks from their website but it appears that they have already taken them down."
The Kush Expo, which is advertised as "the world's biggest medical marijuana mega show," is scheduled for July 6-7 at the Anaheim Convention Center.