Cannabis stocks took a beating last week as fraud allegations against CannTrust (CTST - Get Report) resulted in a mass selloff across the entire sector. 

But that selloff is actually a buying opportunity, according to Jeff Mascio, CEO of Cannabis One, which is a multi state operator (MSO) that itself invests in small cannabis brands and provides them with the scale necessary to grow. 

In our Ask the Expert series, Mascio said, "I would be looking to invest at this time simply because we have seen a compression in the market caps that exist today in cannabis."

"But in doing so, you have to be careful as a retail investor to make sure that you are picking the winners, and that is often times is a difficult thing to do in an emerging market," he added.

Mascio's solution for that problem? ETFs

To hear his full comments, check out the video above. 

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