Can an employee be terminated for decreasing their work hours?

Hello,
We have an employee who was hired for full-time hours (37.5 hours per week) and is now requesting they only be scheduled for two days a week. This does not work for our business needs as we rely on this employee to provide us with full-time hours. The employee is not requesting the decrease due to a medical issue, it is a preference rather than a need. Can we part ways with the understanding that they were hired for full time hours and cannot meet that commitment?
Thank you