As the cannabis industry grows, generating an estimated $10 billion in annual sales, states are increasingly approving medical marijuana programs and passing adult-use laws.

But for marketing agencies, marijuana dispensaries and cannabis brands, advertising the pot brings its own hurdles.

Online platforms with prime advertising space like Facebook and Google do not allow drug, or drug-related promotions on their sites, leaving a large share of marijuana advertising to blogs and podcasts, newsletters and print media. And while experts say Facebook and Google — which control the lion’s share of digital advertising in the country — are unlikely to change their policies until pot is legalized at the federal level, and television and radio come with their own sets of rules, industry members are left to navigate a complex web of state-by-state regulations.

“You would think that Facebook and some of these online platforms are the ideal platforms for these products because you can target only legal states, target only people over 21,” said Aaron Smith, executive director of the National Cannabis Industry Association. “We would gladly follow those guidelines.”

According to Facebook’s policy, ads cannot promote the sale or use of illegal, prescription or recreational drugs. That includes images of recreational or medical marijuana — even in places where the drug is legal.

A Google spokeswoman said marijuana ads are not allowed on the site because the drug is still illegal at the federal level.

The policy applies to all Google ads, as well as other sources like in-app ads and video ads.

Twenty-nine states and the District of Columbia have medical marijuana programs, and eight states plus the District have adult-use laws on the books, according to the National Cannabis Industry Association.

Olivia Mannix, founder and CEO of Cannabrand, a cannabis marketing agency, said she has pushed back on Facebook and its policy, arguing that many patients who could benefit from medical marijuana can’t easily access the information they need. As for the companies Cannabrand works with, Mannix said her team has to think out of the box to reach online customers without targeted ads.

That can include engaging people with wide followings on social media, or even a marijuana-themed Emoji keyboard that features cannabis products and brands.

“You really need to be strategic and creative to get followers because you can’t just put an ad out to get followers,” Mannix said.

Smith said Facebook has rejected or taken down cannabis-related ads and posts inconsistently and that requests for an updated advertising policy have gone unanswered.

Facebook did not return a request for comment.