A new rule prohibiting some Metrolinx employees from using cannabis while off-duty is drawing criticism from the union representing those workers, which plans to explore possible legal challenges to the policy.

"This Metrolinx action shows a profound lack of respect for the men and women who work for it and who devote their working lives to the safety of the public," read a statement sent out by the Amalgamated Transit Union, Local 1587.

This week, Metrolinx updated its 'Fit for Duty' policy to ban cannabis use by employees in "safety sensitive positions." The prohibition applies to those workers whether they are on or off-duty, Metrolinx CEO Phil Verster said in an email statement.

"Recognizing the safety-sensitive nature of Metrolinx's operations and workplace, the Fit for Duty policy establishes Metrolinx's requirements, expectations, and obligations in respect of employee fitness for duty," the statement read.

The regional transit agency employs some 3,700 people.

'What will be next, a ban on off-duty alcohol use?'

Chris Broeze, president of the Amalgamated Transit Union, Local 1587 said in her statement that it is "extremely disappointing to watch Metrolinx focus on the private lives of members.

"Banning responsible marijuana use off-duty does nothing to improve safety. What will be next, a ban on off-duty alcohol use?"

Recreational cannabis use has been legal since October 2018, and the union points out that there have been "zero incidents" involving cannabis and safety among its members.

John Di Nino, national president of the Amalgamated Transit Union, said the "hugely invasive policy" would likely apply to the vast majority of Metrolinx employees.

"My phone has been ringing out off the hook with members who are concerned about how this infringes on their rights," he said in a phone interview on Sunday.

Di Nino said the policy overhaul was completed without any consultation with the union. Its leadership will be exploring the possibility of fighting the changes in court.

"We will be looking at every legal option and every legal challenge possible to protect our members' constitutional rights," he said.