Following the Constitutional Court's 
   Prince judgment, cannabis use, possession and cultivation in South Africa has been decriminalised with adult persons now permitted to use, possess and cultivate cannabis in a private place for personal consumption. (See 
   Minister of Justice and Constitutional Development and Others v Prince; NDPP and Others v Rubin; NDPP and Others v Acton and Others [2018] ZACC 30). Given that 
   Prince does not deal with the effects of the decriminalisation of cannabis in the workplace, many unanswered employment related questions emerge which we set out below. 
What can be said, at this stage is that 
Prince does not affect an employer's obligation to maintain a safe working environment for all of its employees, which includes prohibiting employees who are "intoxicated" from entering the workplace, and policies and testing applicable to alcohol use in the workplace are not likely to be appropriate in dealing with cannabis use.
Cannabis in the workplace
In  terms of Prince, the use, possession  and/or cultivation of cannabis by adults is permitted "in private".  Although cannabis use, possession and cultivation is not confined to  one's "home" or a "private dwelling", it is likely to be  difficult for an employee to argue that the workplace is a "private"  space, especially given that the use of cannabis in public or in the presence  of non-consenting adult persons is not permitted.
  The  more difficult issue is where employees use cannabis in private, outside of the  workplace, and thereafter report for duty. Cannabis can affect an employee's  occupational capacity in various ways, including performing tasks more slowly, performing  poorly when handling routine, monotonous tasks, difficulty in multi-tasking, difficulty  in taking instructions from superiors, difficulty in making crucial decisions  (especially in high risk situations), difficulty in operating machinery and/or  motor vehicles.  It is these consequences  that an employer will have to consider when the employee reports for work and  test positive for cannabis use.
  The  above scenario may not seem very different to employees using alcohol in  private and then reporting for work.  The  difference, however, between alcohol and cannabis in relation to workplace  policy is that for as long as alcohol is detected in the human body, it results  in impairment; Cannabis may be detected in the human body for months after use,  which at that time may no longer cause impairment.
Testing of employees for cannabis
Medical testing of  employees remains regulated by section 7 of the Employment Equity Act (EEA).  Medical testing of employees is permitted if it is justifiable in light of  medical facts, employment conditions, social policy, the fair distribution of  employee benefits or the inherent requirements of a job.  An employer who wishes to test an employee for cannabis may be able to justify  such testing relying on the provisions of the EEA.  A number of tests (some of which are not  available in South Africa at present) are used to test for cannabis: breath,  blood, oral fluid (saliva), urine, sweat and hair. 
  Saliva  tests will show cannabis use in the past 24 hours (which could be an indication  that the employee is still impaired) but hair testing will show cannabis use  for up to months after use (which could mean that the employee is no longer  impaired).  It will not necessarily be  the actual testing that will be problematic, but what one does with the test  results.
Workplace policies and procedures
  Most  employers enforce a zero tolerance approach to the use of any drugs and/or  alcohol in the workplace. Prior to Prince it was relatively easy to deal with cannabis at work as cannabis use,  possession and cultivation was a criminal offence.  Following Prince,  and given that traces of cannabis may remain in the body for months after use  (which does not automatically result in impairment) employers may need to  regulate cannabis as a separate issue and by implication through a separate  policy and procedure. Zero tolerance policies may not be justifiable.
Employers  and their occupational medical practitioners should consider the safety  requirements at the workplace and determine whether a zero tolerance approach  is justifiable or whether there is an acceptable limit of cannabis trace after  some time of use.  This may include  conducting a screening test (such as a saliva test) that will show immediate  past use and then conducting further tests to establish the level of  impairment.