Proponents of marijuana legalization in the U.S. have long eyed California as a place where a legal weed market would thrive. With 39 million residents, it could become the country’s largest retail marijuana market.

It could also be the first to deliver marijuana to customers via drone. San Francisco-based Trees is planning to expand its delivery options to include drones. According to the International Business Times, Trees is “working on a prototype with a drone company and is hoping to bring line of sight deliveries, followed by direct customer deliveries.”

Of course, there’s a couple problems before Trees’ weed-delivering drone takes flight: drone delivery isn’t legal in the United States, and it may never be. The Federal Aviation Administration (FAA) is still working on that. And marijuana use hasn’t been completely decriminalized in California, thought the state was the first to approve medical marijuana use back in 1996.

“We’re not sure when we’ll be launching yet,” a Trees spokesperson says. “We are based in San Francisco and the legal situation here is not clear yet.”

If drone delivery is ever approved, Amazon recently provided some insight as to how to safely integrate drones into the sky. The retail giant proposed that airspace from 200-400 feet off the ground be exclusively reserved for delivery drones. The next 100 feet above that would be a no-fly zone, acting as a buffer between the drones and commercial aircraft.

Delivery drones would also have to be equipped with certain technologies, including GPS, reliable Internet, collision-avoidance sensors and more to ensure drones to collide with each other in mid-air.