I don't see bringing back as an issue at all, if you are with in the legal quantity limits and don't appear to be bringing in for anything other than personal use. Not sure on present restrictions from Cuba are, but that is about the only tobacco or alcohol country that you would actually want to bring something back from that might be restricted. If anything it is a tax and duty issue. In my last two trips I haven't even been asked what I would be declaring, and did not even slow down leaving the baggage area noting that we are just carry on. Noting that MJ is a US Customs Broker and I am in the international freight forwarding world we declare anything and everything when asked.