Canopy Growth operations in Smiths Falls, Ontario. Tom Franck | CNBC

Goldman Sachs star beverage and tobacco analyst Judy Hong was hoping to do some early research into the multibillion-dollar cannabis industry — that is, until she was stopped by the investment bank's firewall blocking certain content. Among the companies the 20-year Goldman veteran tried to review was KushCo Holdings, a California-based business that sells packaging, containers and other supportive products to the world's largest cannabis producers. And though no part of KushCo's business actually touches a marijuana or hemp plant, Hong found herself nonetheless barred from the company's website, said a KushCo executive familiar with the matter. Bank of America Merrill Lynch's consumer analyst is also researching KushCo and the space, the person added. Both Goldman Sachs and Bank of America Merrill Lynch declined to comment about their plans for future marijuana-related research coverage. The KushCo executive said it's fielded calls and met with representatives of both banks.

Wall Street is discovering a unique set of hurdles as it explores the possibilities in cannabis. Those hurdles are in the form of lending restrictions, disagreeing local laws and their own internal company firewalls as banks rush to cover that new and growing market. It is a market that could one day be worth $150 billion globally when including the different derivative products like CBD-infused beverages, according to Tilray CEO Brendan Kennedy. Tilray is a medical marijuana grower based in British Columbia. Other challenges for Wall Street include the flurry of federal regulations that currently deter banks from working with legal dispensaries in the U.S. and mandate that banks and other financial firms file "suspicious activity reports" to help monitor money laundering. Others have brought the just-say-no attitude to Wall Street, steering clear of any services related to the marijuana business for fear of federal prosecution.

Reputation risk?

Martin Landry, a Canadian equity analyst at GMP Securities, told CNBC that his first interaction with the cannabis industry came in 2013 when his firm helped Canopy Growth conduct a round of private financing. Canada became the first Group of Seven country to approve recreational use of pot when Ottawa passed legislation in October. "I was covering consumer and some pharma names and [my company] asked if I would look at the sector. And I said 'no,'" Landry said Friday. The analyst explained that he shied away at first for fear that the other consumer and pharmaceutical companies under his coverage wouldn't take him as seriously and that the new venture could damage his existing reputation. It was later that he eventually decided to explore coverage on Canopy, Cronos Group and other industry names.

But for those willing to take a chance, the cannabis industry could represent a sizable revenue stream. Some experts, such as Cowen's Vivien Azer, see the U.S. marijuana market growing to $80 billion by 2030. The up-and-coming market has attracted investments from a range of people and companies looking for the help of big banks. That is a group including venture capitalist Peter Thiel and the globe's largest alcohol companies looking for a strategic partnership. Azer is one of just three analysts from a major brokerage covering the space currently.

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