Supporters of marijuana legalization are elated about the passage of Proposition 64, which will allow anyone 21 and older to buy recreational pot from licensed California sellers starting Jan. 1, 2018.

Or will it? Some officials say that the start date might have to be pushed back because the state agency that will regulate growers, producers and pot shops won't have the regulations required by state law in place by then. In fact, the Bureau of Medical Cannabis Regulation needs to establish not only how recreational shops are licensed and permitted but also how the multibillion-dollar product is grown, tracked and tested.

“It's taking so long to get the draft regulations out there,” says Dale Gieringer, director of California NORML. “It wouldn't surprise me if they're late. Furthermore, there's every indication the Legislature will pass some more bills altering the regulatory system this year, which could require a midstream adjustment that would further push legal sales down the line.”

State Sen. Mike McGuire, head of the Senate Governance and Finance Committee, told the Sacramento Bee that delays are probable and that some businesses would open anyway. “But is it a licensed business?” he asked.

Yet Alex Traverso, spokesman for the Bureau of Medical Cannabis Regulation, insists recreational sales will start on Jan. 1. He says regulations will be sent to the state Office of Administrative Law in March, after which the public will have 45 days to offer feedback. “The Jan. 1 deadline is mandated by law, and we have every intention of meeting it,” he says.

The work is being spread among state bureaucracies: The Department of Food and Agriculture is focused on grow regulations, the Department of Public Health is focused on manufacturing (including edibles), and the Bureau of Medical Cannabis Regulation is developing rules for retail and testing lab licenses, Traverso said.

There are elements of the process that could make it more difficult to make the deadline. Traverso acknowledges that public feedback could inspire a major reworking of the regulations (which would then require another round of feedback), while unforeseen legislation could rewrite the rules or reshape the process.

Organizers of Proposition 64 expressed optimism that the bureau would be able to pass the regulations on time — largely because they can be based on existing rules for medical marijuana passed by the Legislature in 2015.

“This didn't start from scratch,” says Lynne Lyman, state director of the Drug Policy Alliance, which helped write Proposition 64. “A lot of the work has already been done.”

Like Lyman, Jason Kinney, spokesman for the now-concluded Yes on 64 campaign, points out that the heavy lifting of regulation-writing already has been carried out by 2015's Medical Cannabis Regulation and Safety Act, which will require medical pot shops to obtain state and local licenses by Jan. 1.

“Proposition 64 was written to find conformity where [it] can, not having two people doing the same thing,” he says. “There's no wheel-reinventing going on.”

Tens of millions of dollars in 2016 and 2017 have been earmarked by Gov. Jerry Brown to help implement new medical and recreational regulations. Any delay would add up to huge disappointment and big monetary losses for a wave of marijuana entrepreneurs who see California as a potentially explosive legal drug market come 2018. Investments are on the line.

“The DPA is pushing hard for on-time implementation,” Lyman says. “Not doing so would leave us in the same gray-market state we've been in for 20 years.”

She argues that legalization proponents should fear President Trump more than California's sometimes-slow bureaucracy. Trump's choice for attorney general, Jeff Sessions, has expressed disdain for cannabis.

“If Trump sends in the feds to shut down dispensaries, it might not make sense to issue licenses,” Lyman says. “To me that's a much bigger question mark.”