Hi 1981Leigh,
Most industrial courts and tribunals recognise that random drug testing intrudes on the privacy of the individual. Therefore, it is only justified on grounds of health and safety. Your employer will have a legitimate right to test for drugs or alcohol in an attempt to eliminate the risk that employees might come to work impaired by such substances and posing a risk to health and safety. However, such testing would need to comply with the International Labour Organisation code of practice on the management of alcohol and drug-related issues in the workplace. However, beyond the cause of health and safety, an employer has no right to dictate the alcohol or drug taking habits of its employees in their own time.