Just a few weeks ago, the Oracle of Omaha, Warren Buffett, wrapped up another highly successful annual shareholder meeting for the conglomerate he's run for decades, Berkshire Hathaway (BRK.A 0.55%) (BRK.B 0.50%). This event has become something of a mecca for investing enthusiasts, allowing them to listen to what one of the most successful buy-and-hold investors in the world has to say about the stock market, the economy, and other financial matters.

But just as investors have flocked to Buffett's favorite stocks and industries for decades, they also take note when he shows skepticism toward a company, industry, or trend.

Berkshire Hathaway CEO Warren Buffett speaking with reporters at the company's annual shareholder meeting.

Berkshire Hathaway CEO Warren Buffett. Image source: The Motley Fool.

Buffett and cannabis don't mix

Despite arguably being one of the fastest growing industries, marijuana isn't exactly "high" on Buffett's buy list. To be clear, it does offer some traits that Buffett would probably appreciate, such as the likely noncyclical nature of cannabis consumption, and the fact that you don't have to dive headfirst into a grower in order to gain exposure. But when examined as a whole, there's a veritable laundry list of reasons Buffett would stay away from pot stocks rather than be a buyer.

For example, he traditionally buys into time-tested, profitable business models. The fact is that a majority of pot stocks are still losing money on an operating basis, and the industry hasn't demonstrated that it has staying power.

Another pervasive problem is that Buffett and his team generally don't want to have to babysit their holdings. He prefers to buy companies that can essentially be set in Berkshire Hathaway's portfolio and forgotten about for years. With the legal status of marijuana different in many countries and changing constantly, buying into pot stocks would require a lot of upkeep that Buffett simply isn't willing to give.

Also, don't overlook that most pot stocks are still listed on the over-the-counter (OTC) exchange, rather than a major U.S. exchange. Neither the New York Stock Exchange nor Nasdaq will allow companies that sell a federally illicit substance in the United States, such as marijuana, to list their common stock. Buffett, for his part, only cares to purchase stock in companies that are listed on major exchanges.

As I said, there's a pretty long list of reasons for Buffett to not buy marijuana stocks.

A rolled cannabis joint lying atop a cannabis leaf.

Image source: Getty Images.

But Buffett already has marijuana investment exposure!

Recently, he doubled down on his anti-cannabis rhetoric when asked by Fox Business Network anchor Liz Claman about the possibility of Coca-Cola getting into the marijuana industry. Said Buffett: "It would be a mistake for Coca-Cola to get into the marijuana-cannabis business. They have a wholesome image, and that would be detrimental to it."

Yet, what you might find surprising is that of 47 separate securities that Berkshire Hathaway owned at the end of the first quarter, at least a handful of them already have some degree of marijuana industry exposure.

As noted by my Motley Fool colleague Jason Hall, nearly $95 billion of Berkshire's $199 billion in total investments as of the end of the first quarter were in financial services companies, including big investments in Bank of America (BAC 0.92%), Wells Fargo (WFC 0.92%), and JPMorgan Chase (JPM 0.50%). As of this past weekend, Berkshire owned almost $25.5 billion worth of Bank of America stock, $18.7 billion worth of Wells Fargo stock, and $6.6 billion of JPMorgan Chase stock.

What makes these particular names stand out from the crowd is that in select U.S. states, they have been allowing marijuana businesses to set up checking and/or savings accounts, as well as gain access to basic banking services, which includes traditional loans and lines of credit.

A cannabis leaf atop a neat stack of hundred dollar bills.

Image source: Getty Images.

According to a study released in early 2017 that was commissioned by the journal American Banker, 34% of businesses that filed to operate a medical marijuana dispensary in Massachusetts between June 2015 and September 2016 had a bank account with one of the United States' big-four banks: Bank of America, Wells Fargo, JPMorgan Chase, or Citigroup, which is the only large bank Buffett's Berkshire Hathaway doesn't currently own. The study further notes that Bank of America appeared to be the most accommodating, with a little more than half of all medical cannabis applicants having an account with the bank.

This is an interesting finding given that cannabis is still a federally illicit (i.e., Schedule I) substance, and therefore most banks would be expected to avoid helping marijuana business altogether for fear of facing criminal prosecution and/or financial penalties. A banking bill working its way through Congress (the SAFE Banking Act) offers hope that new banking doors will open to the U.S. pot industry in the months and years to come.

The point here being that while the aggregate exposure in revenue dollars to the marijuana industry is likely very small, Buffett's financial-services-heavy portfolio does have at least some cannabis exposure.

Down the line, there are other avenues beyond banking that could increase Buffett's cannabis exposure. For instance, snack maker Mondelez International has talked about using cannabidiol (CBD), the nonpsychoactive cannabinoid best known for its perceived medical benefits, in its popular Chips Ahoy cookies, Cadbury chocolates, Nilla wafers, and Nutter Butter cookies. Berkshire currently holds a $30 million stake in Mondelez. 

Whether Buffett is ready or not, cannabis is liable to play a role in the performance of Berkshire Hathaway's investment portfolio.