With the rise in the use of Medicinal Cannabis (and its occasional abuse), it has become increasingly important for workplaces and workers to understand the issues associated with its use, and the necessity to consider the possible risks it brings to the workplace. 
This workplace safety poster emphasises the responsibility of those on this medication to let the workplace know so they can assess and manage any risks posed by them being on it - just as they should do with any other medication that can affect their performance such as "not operating heavy machinery".
 
The information in this poster is gleaned from various Safety Regulators around the world, and is general in nature. You should  therefore ensure it is relevant to your particular jurisdiction.