What is “just cause?”
Just cause is a term of art in employment law. An employee terminated for just cause is not entitled to severance or notice. With that being said, if your employer asserts "just cause" to fire you, it does not mean they are right.
The seminal case on the issue is McKinley v BC Tel, where the Supreme Court of Canada ruled that just cause could only be evaluated with reference to the specific context of each given case.
Just cause is defined in many ways in the case law, but (broadly speaking) it tends to fall into one of two categories:
1. minor misconduct which the employer specifically notifies the employee must be improved upon; or
2. misconduct which is so egregious that no warning is required.