In Melbourne, Deputy President Anne Gooley rejected the union's claim that the plan would result in a "health and welfare approach" to drug issues, saying it simply changed the decision-maker on disciplinary action from the employer to the show cause group.
The AMWU applied for the Commission to deal with a dispute relating to the consequences of returning a first positive drug and alcohol test under employer ACI Operations Pty Ltd's proposed workplace drug and alcohol policy.
The drug and alcohol policy stated that while a worker's "first positive test result will generally result in a caution, each case will be treated on its own merit and other disciplinary action may also be taken following a confirmed positive result".
The union argued the policy should be amended so that a worker who failed a test was referred to a show cause group – made up of a manager or supervisor, an employee representative and an HSR – to determine what, if any, disciplinary action should be taken.
"This would result in a health and welfare approach to issues of drug and alcohol use being adopted rather than a disciplinary approach," it said.
It also said discipline wasn't appropriate if a worker tested positive for drugs or alcohol but wasn't impaired, and workers should be "given the skills and information to correct [their] behaviour".
ACI opposed the union's proposal, arguing the current policy had a number of provisions to help workers manage drug and alcohol issues, such as providing testing devices in the car park so they could self-test before reporting for work.
It said a show cause group would result in unnecessary cost and delay, and that if the group assessed someone as fit to work, and that worker had a workplace accident, "then issues as to liability under health and safety legislation would arise".
Deputy President Gooley found the AMWU's major concern was that a worker might receive more than a caution for a first positive test result even if they didn't display any "obvious impairment".
But its proposal went beyond remedying this concern by making the show cause group "the arbitrator of the disciplinary outcome in all cases", she said.
"The AMWU process would apply even where an employee has returned first positive test as a result of a show cause test or a test that occurred as a result of a serious or potentially serious incident," she said.
"I do not consider that the show cause group is an appropriate body to determine the disciplinary response to a first positive test."
Deputy President Gooley added that the "deeply personal nature" of the reasons workers misused drugs and alcohol shouldn't be disclosed to more people than was necessary.
"I do not accept the submissions of the AMWU that its proposal provides for a health and welfare approach to be adopted as opposed to a disciplinary approach. All the AMWU's proposal does is change the decision maker from ACI to the show cause group," she said.
Australian Manufacturing Workers' Union (AMWU) v ACI Operations Pty Ltd  FWC 3162 (7 May 2015)