Choice of Forum: Grievance Process vs Human Rights
The issue as to the right of a unionized worker to use the human rights process, as noted in the above post, is complicated and varies based on the jurisdiction.
The first question is why a union member would prefer to use the human rights administrative process.
A labour arbitrator is, of course, allowed to set human rights remedies and also may award independent sums for aggravated and/or punitive damages, in addition to awards for personal injuries as human rights damages.
The arbitral process is generally much faster than the human rights process. Also, reinstatement is considered the default remedy in labour jurisprudence, whereas it is discretionary in human rights cases.
The union will also provide competent legal counsel to represent the employee. A human rights case will require the employee to fund their legal counsel.
These factors all favour the use of the grievance process.
Presumably, this issue may arise where the union does not support the grievance and the collective agreement mandates union support for it.
Also, the complainant may wish to add the union as a respondent to the human rights complaint, asserting that the decision not to advocate for the grievance is, in itself, a human rights violation.
Where the law allows for concurrent jurisdiction in exceptional circumstances, such as in Alberta, this may present such an argument.
In addition, the union may have missed the limitation period for grievance presentation as set out in the collective agreement, which again may be argued as an exceptional circumstance.