Drug testing in the work place
As an employer, you can unilaterally introduce drug testing in your workplace even if it is not expressly provided for in the employment agreement but the drug testing policy must be reasonable and your employer should consult staff before implementing the policy.
What is reasonable will depend on the circumstances of your workplace. Drug testing in New Zealand will be regarded as reasonable only in relation to workplaces which contain "safety sensitive areas". This means there must be a close connection between performing your duties under the influence of drugs/alcohol and operational safety.
There has been recent court rulings regarding this subject such as NZ Amalgated Engineering and Manufacturing Union v Air NZ and MUNS and Ors v TLNZ.
However, the Courts have stated that as the employers must explain the reasons for the policy, how the testing will be carried out, the procedure for consent to testing, the consequences of refusing consent (ie disciplinary action), the type of testing (breath/urine/blood), and the possibility of medical review of test results. It is recommended for further impartiality, testing should be carried out by a reliable external agency.
HR Tool Kit:
Workplace Medical Issues
Alcohol and Drugs
HR Resource - Workplace Drug Testing
Employment Court Case Law