The big can of worms that will be opened up in regards to employment matters is one of the principal reasons why I support a no vote. I really wouldn't want to be a test case for an employees actions whilst he had legal THC in his / her system. ERA in one corner looking to pound on you if you do take some sort of action, worksafe in the other if anything goes wrong because you didn't take action.
If you are happy for a sparked up electrician to come and rewire your house risking all manner of electrical hazards, thats your right, but I'll take a hard pass