Back many many moons ago in the year 2008 I traveled to the great city Vancouver to see a friend. They took me to a venue to see a band and cigarette smoking wasn't allowed.
But you bet your fucking ass there was plenty of people smoking weed. Which seems to be just fine...breathing in second hand smoke...which is the main reason these tabacco restrictions are in place.
EDIT
I don't care if you smoke weed, only it has the same second hand smoke issue tabacco does and should follow the same rule.