Thank you for your inquiry. This is a very important area of law in terms of growing/expanding cannabis brands in the U.S. and world. I speak on this issue a lot, as we have successfully helped some of the largest cannabis brands expand across state lines, without selling cannabis across state lines. The strategy involves a multifaceted and strategic approach, which we won't get into here. But, to your question, it all starts with a solid foundation, which are protectable and enforceable trademark rights.
As you likely know, the United States Patent and Trademark Office (USPTO) governs federal trademarks in the United States. These powerful IP rights cover products and services involved in interstate commerce (good/services sold across state lines). Each state also provides for its own trademark protection for goods and services that are, similar to cannabis businesses, conducted solely intrastate (within state lines). And, finally, you have trademark rights owned in Common Law, which are unregistered trademarks, but which are also enforceable against infringement if one can prove date of first use and ongoing use in intrastate or interstate commerce.
Based on the aforementioned, and that cannabis is not in lawful use in the U.S. (federally), you cannot obtain a federally registered trademark from the USPTO for any cannabis product. And, unfortunately, many states, like California, for example, take their direction from the USPTO. They will lure you in to apply for a state level trademark and take your fees, but in the end they will deny your applications, based on the USPTO's determination that the goods (cannabis) are not in lawful use in the U.S.
So, how do we get around this issue. Well, we have been very successful in helping clients build some of the most well known brands in the industry by securing federally registered trademarks for tangentially related goods and services to their cannabis good or service, that through trademark law will also protect them in the space that matters most, the actual cannabis good or service. It is by using this strategy, and only this strategy (at this time), that you can build a valuable cannabis brand that can be used throughout the U.S. and world.
There are also a number of other ways you can protect and leverage your unregistered intellectual property (trade dress, for example), including licensing, that will help you build a great brand in the cannabis industry. If you are interested, I spoke on this exact topic at this year's NCIA Business Summit in Oakland. You can access the NCIA for copies of all presentations.