Google doesn't allow ads that promote the use, sale, or even provide informational content about cannabis. Well, it's kind of a process, but it's possible to run ads on Google for marijuana companies. We do this for several customers and are having a good success. It's not allowed to advertise CBD on Google if the oil is made from cannabis, but technically it's OK if it's made from hemp.
This ambiguity makes it risky to invest in Google advertising campaigns, since you risk being excluded by Google.