Correct. Employees can’t choose their return date if they’re in COVID mandated self isolation. More precisely, they definitely aren’t allowed to shorten it; however, they may be able to extend it IF they have grounds for additional leave under the ESA or their contract/collective agreement. In other words, once the 14 days expires, the need for leave ends and they must return. However, something else might have happened that itself constitutes grounds for leave. Maybe a close family member got sick, for example.
Bottom Line: Ask the employee WHY he/she isn’t coming back after the 14 days. If he/she claims it’s due to another leave, require verification. If he/she doesn’t have justification, you can insist he/she return after the 14 days. Or maybe give them the option of using vacation days. But they can’t dictate when their isolation leave ends.