Even though marijuana has been legalized in California, the folks behind the Coachella festival won't let fans bring it into the two-weekend event.
The festival's website says, "Sorry, bro. Marijuana and marijuana products aren’t allowed inside. Even in 2018 and beyond. If that changes, we’ll update this answer."
Even though the festival take place on the privately owned Empire Polo Grounds, the festival organizers probably don't want to strain relations with leaders of Indio, California. The city is one of the localities in the state that still considers pot illegal. Coachella is set for the weekends of April 13th and 20th.