Yeah, refusing the package is your best bet. You could also accept the package, and don't open it. If you do get searched, you could simply say you were expecting something else in the mail, and thought this was it. When you recieved the package, you saw it wasn't for you....just don't open it for a couple days to be on the safe side.
If you don't mind the $$ loss, refusing would be the best bet. Just make sure your house/computer are "clean"