With the understanding that I’m not allowed to offer you legal counsel, my personal suggestion would be to ask the employee to clarify his/her position. Questions: Are you formally refusing to return? If so, on why?
If the answer is safety-related, ask if he/she is engaging in an OHS work refusal and to give his/her reasons why he/she thinks there’s a danger.
If the answer is due to a disability, ask if he/she is requesting an accommodation and for what disability.
If the answer is based on preference, check the terms of the employment agreement and see if he/she has telecommuting rights.
Once you know what you’re dealing with, you can decide how to proceed. Feel free to circle back with me at that point if you need further help. Meanwhile, here’s some of the many things we’ve written on this topic for HRI.
https://hrinsider.ca/quiz-may-employees-refuse-to-return-to-the-post-covid-19-workplace/
https://hrinsider.ca/return-to-work-managing-employee-reluctance-and-refusals/
Hope that helps. Glenn