[ARCHIVE ANSWER]
Correct. They will stop a human from smelling it but not a dog. It has to be “vapor proof,” meaning not a molecule can pass through the bag or container. If you notice those bags will let freezer burn happen after awhile, this means water vapor is passing through the bag. Like I said, they do make good vapor proof bags that work in the "seal a meal" vacuum sealer. It's a cellophane-type material. You can Google up places that sell them. If you ever seen catfish bait at the bait shop, it's the same stuff.
A med patient I know was just busted sending two ounces in the mail to his friend.
It was double-vacuumed sealed, and the dog still smelled it. Now I can't tell you how careful the sender was not to contaminate the outside of the package though.
I'm guessing that was the cause. I'm thinking double vacuum bags would work for a short period of time, but I've never tested it myself and wouldn't take the risk with my freedom without testing it myself first.