I'd say absolutely NO. No federally "illegal" drugs are allowed on any cruise ship, "medicinal" or not.
That's not to say that I haven't smelled an "unusual" odor on a cruise, but if you're caught you'll be in serious trouble!
You may find yourself in a jail in a foreign port , or you may be thrown off the ship to find your own way home.
IMO, don't try it!
__________________
Fern
"A truly happy person is one who can enjoy the scenery on a detour."
Carnival Inspiration 2002 Carnival Elation 2004
Grand Princess 2004 NCL Sun 2005
Sun Princess 2006 NCL Dream 2007
Caribbean Princess 2007 NCL Dawn 2008
Island Princess 2008 Island Princess 2009
Golden Princess 2009 Carnival Conquest 2010
Grand Princess 2010 Island Princess 2011
Grand Princess 2011 Carnival Magic 2012
Carnival Dream 2012 Island Princess 2013
I wouldn't advise trying it either. I've read occasional stories of people who were deported from the ship into the hands of the police at various ports -- not a pretty situation.
Also, when you disembark from the ship, the customs agents do use dogs. All the luggage is lined up in rows so that their furry, 4-legged agents can walk between the suitcases to detect any unusual items. Not worth it in my estimation.