Under human rights law, individuals that suffer from addiction are protected under prohibited grounds of discrimination. For this reason, any policy that has an adverse effect on employees with addictions will have to be a bona fide occupational requirement (BFOR).  This means that employees found in violation of such policies will have to be accommodated for up to the point of undue hardship.
For a job requirement or workplace policy to qualify as a BFOR, it first has to rationally connect to the performance of the job. For random and unannounced drug/alcohol testing in a safety sensitive environment, the goal would be that the employees performing the job are doing so under conditions that do not compromise safety. The condition of sobriety definitely rationally connects to the objective of workplace safety. Secondly, the policy has to be implemented with honesty and good faith. In this instance, it is reasonable to believe that random testing is a tool that would contribute towards a safer working environment in safety sensitive workplaces.
Lastly, the policy must be reasonably necessary to accomplish the objective of workplace safety. To establish this, it must be shown that not only is the policy necessary, but that impaired individuals cannot be accommodated without the employer suffering undue hardship. This requires exploring possibilities such as modifying tasks or providing alternative work. For workplace that is safety sensitive, there may not be alternatives to accommodate those unable to perform work in safety sensitive roles. It is always best to consult with an employment law expert when seeking to accommodate with minimal options. At the very least, an attempt must be made by the employer.
In terms of policy, employers should be cautious when implementing random drug testing. Methods of testing that do not measure present impairment will be found to be in violation of human rights. Methods of testing must be able to test for present impairment because this is a direct measure of an individual’s ability to perform while on the job. In the eyes of the law, measuring past impairment discriminates against those with addiction, while providing little indication of their present ability to perform their jobs safely.